diff --git a/services/backup/src/constants.rs b/services/backup/src/constants.rs
index 29a16c522..d4d58aca0 100644
--- a/services/backup/src/constants.rs
+++ b/services/backup/src/constants.rs
@@ -1,32 +1,32 @@
 // Assorted constants
 
 pub const MPSC_CHANNEL_BUFFER_CAPACITY: usize = 1;
 pub const ID_SEPARATOR: &str = ":";
 pub const ATTACHMENT_HOLDER_SEPARATOR: &str = ";";
 
 // Configuration defaults
 pub const DEFAULT_HTTP_PORT: u16 = 50052;
 pub const DEFAULT_BLOB_SERVICE_URL: &str = "http://localhost:50053";
 
 // Environment variable names
 pub const LOG_LEVEL_ENV_VAR: &str =
   tracing_subscriber::filter::EnvFilter::DEFAULT_ENV;
 
 // DynamoDB constants
 
 pub const BACKUP_TABLE_NAME: &str = "backup-service-backup";
 pub const BACKUP_TABLE_FIELD_USER_ID: &str = "userID";
 pub const BACKUP_TABLE_FIELD_BACKUP_ID: &str = "backupID";
 pub const BACKUP_TABLE_FIELD_CREATED: &str = "created";
-pub const BACKUP_TABLE_FIELD_RECOVERY_DATA: &str = "recoveryData";
-pub const BACKUP_TABLE_FIELD_COMPACTION_HOLDER: &str = "compactionHolder";
+pub const BACKUP_TABLE_FIELD_USER_DATA: &str = "userData";
+pub const BACKUP_TABLE_FIELD_USER_KEYS: &str = "userKeys";
 pub const BACKUP_TABLE_FIELD_ATTACHMENT_HOLDERS: &str = "attachmentHolders";
 pub const BACKUP_TABLE_INDEX_USERID_CREATED: &str = "userID-created-index";
 
 pub const LOG_TABLE_NAME: &str = "backup-service-log";
 pub const LOG_TABLE_FIELD_BACKUP_ID: &str = "backupID";
 pub const LOG_TABLE_FIELD_LOG_ID: &str = "logID";
 pub const LOG_TABLE_FIELD_PERSISTED_IN_BLOB: &str = "persistedInBlob";
 pub const LOG_TABLE_FIELD_VALUE: &str = "value";
 pub const LOG_TABLE_FIELD_ATTACHMENT_HOLDERS: &str = "attachmentHolders";
 pub const LOG_TABLE_FIELD_DATA_HASH: &str = "dataHash";
diff --git a/services/backup/src/database/backup_item.rs b/services/backup/src/database/backup_item.rs
index f9186fce8..f2ec37270 100644
--- a/services/backup/src/database/backup_item.rs
+++ b/services/backup/src/database/backup_item.rs
@@ -1,78 +1,127 @@
 use aws_sdk_dynamodb::types::AttributeValue;
 use chrono::{DateTime, Utc};
-use comm_services_lib::database::{DBItemError, TryFromAttribute};
-use std::collections::HashMap;
+use comm_services_lib::{
+  blob::types::BlobInfo,
+  database::{DBItemError, TryFromAttribute},
+};
+use std::collections::{HashMap, HashSet};
 
 use crate::constants::{
   BACKUP_TABLE_FIELD_ATTACHMENT_HOLDERS, BACKUP_TABLE_FIELD_BACKUP_ID,
-  BACKUP_TABLE_FIELD_COMPACTION_HOLDER, BACKUP_TABLE_FIELD_CREATED,
-  BACKUP_TABLE_FIELD_RECOVERY_DATA, BACKUP_TABLE_FIELD_USER_ID,
+  BACKUP_TABLE_FIELD_CREATED, BACKUP_TABLE_FIELD_USER_DATA,
+  BACKUP_TABLE_FIELD_USER_ID, BACKUP_TABLE_FIELD_USER_KEYS,
 };
 
 #[derive(Clone, Debug)]
 pub struct BackupItem {
   pub user_id: String,
   pub backup_id: String,
   pub created: DateTime<Utc>,
-  pub recovery_data: String,
-  pub compaction_holder: String,
-  pub attachment_holders: String,
+  pub user_keys: BlobInfo,
+  pub user_data: BlobInfo,
+  pub attachment_holders: HashSet<String>,
 }
 
 impl BackupItem {
   pub fn new(
     user_id: String,
     backup_id: String,
-    compaction_holder: String,
+    user_keys: BlobInfo,
+    user_data: BlobInfo,
+    attachment_holders: HashSet<String>,
   ) -> Self {
     BackupItem {
       user_id,
       backup_id,
-      compaction_holder,
       created: chrono::Utc::now(),
-      // TODO: Recovery data is mocked with random string
-      recovery_data: crate::utils::generate_random_string(
-        20,
-        &mut rand::thread_rng(),
+      user_keys,
+      user_data,
+      attachment_holders,
+    }
+  }
+}
+
+impl From<BackupItem> for HashMap<String, AttributeValue> {
+  fn from(value: BackupItem) -> Self {
+    let mut attrs = HashMap::from([
+      (
+        BACKUP_TABLE_FIELD_USER_ID.to_string(),
+        AttributeValue::S(value.user_id),
+      ),
+      (
+        BACKUP_TABLE_FIELD_BACKUP_ID.to_string(),
+        AttributeValue::S(value.backup_id),
+      ),
+      (
+        BACKUP_TABLE_FIELD_CREATED.to_string(),
+        AttributeValue::S(value.created.to_rfc3339()),
+      ),
+      (
+        BACKUP_TABLE_FIELD_USER_KEYS.to_string(),
+        value.user_keys.into(),
+      ),
+      (
+        BACKUP_TABLE_FIELD_USER_DATA.to_string(),
+        value.user_data.into(),
       ),
-      attachment_holders: String::new(),
+    ]);
+
+    if !value.attachment_holders.is_empty() {
+      attrs.insert(
+        BACKUP_TABLE_FIELD_ATTACHMENT_HOLDERS.to_string(),
+        AttributeValue::Ss(value.attachment_holders.into_iter().collect()),
+      );
     }
+
+    attrs
   }
 }
 
-pub fn parse_backup_item(
-  mut item: HashMap<String, AttributeValue>,
-) -> Result<BackupItem, DBItemError> {
-  let user_id = String::try_from_attr(
-    BACKUP_TABLE_FIELD_USER_ID,
-    item.remove(BACKUP_TABLE_FIELD_USER_ID),
-  )?;
-  let backup_id = String::try_from_attr(
-    BACKUP_TABLE_FIELD_BACKUP_ID,
-    item.remove(BACKUP_TABLE_FIELD_BACKUP_ID),
-  )?;
-  let created = DateTime::<Utc>::try_from_attr(
-    BACKUP_TABLE_FIELD_CREATED,
-    item.remove(BACKUP_TABLE_FIELD_CREATED),
-  )?;
-  let recovery_data = String::try_from_attr(
-    BACKUP_TABLE_FIELD_RECOVERY_DATA,
-    item.remove(BACKUP_TABLE_FIELD_RECOVERY_DATA),
-  )?;
-  let compaction_holder = String::try_from_attr(
-    BACKUP_TABLE_FIELD_COMPACTION_HOLDER,
-    item.remove(BACKUP_TABLE_FIELD_COMPACTION_HOLDER),
-  )?;
-  let attachment_holders = String::try_from_attr(
-    BACKUP_TABLE_FIELD_ATTACHMENT_HOLDERS,
-    item.remove(BACKUP_TABLE_FIELD_ATTACHMENT_HOLDERS),
-  )?;
-  Ok(BackupItem {
-    user_id,
-    backup_id,
-    created,
-    recovery_data,
-    compaction_holder,
-    attachment_holders,
-  })
+impl TryFrom<HashMap<String, AttributeValue>> for BackupItem {
+  type Error = DBItemError;
+
+  fn try_from(
+    mut value: HashMap<String, AttributeValue>,
+  ) -> Result<Self, Self::Error> {
+    let user_id = String::try_from_attr(
+      BACKUP_TABLE_FIELD_USER_ID,
+      value.remove(BACKUP_TABLE_FIELD_USER_ID),
+    )?;
+    let backup_id = String::try_from_attr(
+      BACKUP_TABLE_FIELD_BACKUP_ID,
+      value.remove(BACKUP_TABLE_FIELD_BACKUP_ID),
+    )?;
+    let created = DateTime::<Utc>::try_from_attr(
+      BACKUP_TABLE_FIELD_CREATED,
+      value.remove(BACKUP_TABLE_FIELD_CREATED),
+    )?;
+
+    let user_keys = BlobInfo::try_from_attr(
+      BACKUP_TABLE_FIELD_USER_KEYS,
+      value.remove(BACKUP_TABLE_FIELD_USER_KEYS),
+    )?;
+    let user_data = BlobInfo::try_from_attr(
+      BACKUP_TABLE_FIELD_USER_DATA,
+      value.remove(BACKUP_TABLE_FIELD_USER_DATA),
+    )?;
+
+    let attachments = value.remove(BACKUP_TABLE_FIELD_ATTACHMENT_HOLDERS);
+    let attachment_holders = if attachments.is_some() {
+      HashSet::<String>::try_from_attr(
+        BACKUP_TABLE_FIELD_ATTACHMENT_HOLDERS,
+        attachments,
+      )?
+    } else {
+      HashSet::new()
+    };
+
+    Ok(BackupItem {
+      user_id,
+      backup_id,
+      created,
+      user_keys,
+      user_data,
+      attachment_holders,
+    })
+  }
 }
diff --git a/services/backup/src/database/mod.rs b/services/backup/src/database/mod.rs
index d0cb48fe9..51be41683 100644
--- a/services/backup/src/database/mod.rs
+++ b/services/backup/src/database/mod.rs
@@ -1,308 +1,281 @@
 pub mod backup_item;
 pub mod log_item;
 
 use std::collections::HashMap;
 
 use aws_sdk_dynamodb::{
   operation::get_item::GetItemOutput, types::AttributeValue,
 };
 use comm_services_lib::database::Error;
 use tracing::error;
 
 use crate::constants::{
-  BACKUP_TABLE_FIELD_ATTACHMENT_HOLDERS, BACKUP_TABLE_FIELD_BACKUP_ID,
-  BACKUP_TABLE_FIELD_COMPACTION_HOLDER, BACKUP_TABLE_FIELD_CREATED,
-  BACKUP_TABLE_FIELD_RECOVERY_DATA, BACKUP_TABLE_FIELD_USER_ID,
+  BACKUP_TABLE_FIELD_BACKUP_ID, BACKUP_TABLE_FIELD_USER_ID,
   BACKUP_TABLE_INDEX_USERID_CREATED, BACKUP_TABLE_NAME,
   LOG_TABLE_FIELD_ATTACHMENT_HOLDERS, LOG_TABLE_FIELD_BACKUP_ID,
   LOG_TABLE_FIELD_DATA_HASH, LOG_TABLE_FIELD_LOG_ID,
   LOG_TABLE_FIELD_PERSISTED_IN_BLOB, LOG_TABLE_FIELD_VALUE, LOG_TABLE_NAME,
 };
 
 use self::{
-  backup_item::{parse_backup_item, BackupItem},
+  backup_item::BackupItem,
   log_item::{parse_log_item, LogItem},
 };
 
 #[derive(Clone)]
 pub struct DatabaseClient {
   client: aws_sdk_dynamodb::Client,
 }
 
 impl DatabaseClient {
   pub fn new(aws_config: &aws_types::SdkConfig) -> Self {
     DatabaseClient {
       client: aws_sdk_dynamodb::Client::new(aws_config),
     }
   }
 
   // backup item
   pub async fn put_backup_item(
     &self,
     backup_item: BackupItem,
   ) -> Result<(), Error> {
-    let item = HashMap::from([
-      (
-        BACKUP_TABLE_FIELD_USER_ID.to_string(),
-        AttributeValue::S(backup_item.user_id),
-      ),
-      (
-        BACKUP_TABLE_FIELD_CREATED.to_string(),
-        AttributeValue::S(backup_item.created.to_rfc3339()),
-      ),
-      (
-        BACKUP_TABLE_FIELD_BACKUP_ID.to_string(),
-        AttributeValue::S(backup_item.backup_id),
-      ),
-      (
-        BACKUP_TABLE_FIELD_RECOVERY_DATA.to_string(),
-        AttributeValue::S(backup_item.recovery_data),
-      ),
-      (
-        BACKUP_TABLE_FIELD_COMPACTION_HOLDER.to_string(),
-        AttributeValue::S(backup_item.compaction_holder),
-      ),
-      (
-        BACKUP_TABLE_FIELD_ATTACHMENT_HOLDERS.to_string(),
-        AttributeValue::S(backup_item.attachment_holders),
-      ),
-    ]);
+    let item = backup_item.into();
 
     self
       .client
       .put_item()
       .table_name(BACKUP_TABLE_NAME)
       .set_item(Some(item))
       .send()
       .await
       .map_err(|e| {
         error!("DynamoDB client failed to put backup item");
         Error::AwsSdk(e.into())
       })?;
 
     Ok(())
   }
 
   pub async fn find_backup_item(
     &self,
     user_id: &str,
     backup_id: &str,
   ) -> Result<Option<BackupItem>, Error> {
     let item_key = HashMap::from([
       (
         BACKUP_TABLE_FIELD_USER_ID.to_string(),
         AttributeValue::S(user_id.to_string()),
       ),
       (
         BACKUP_TABLE_FIELD_BACKUP_ID.to_string(),
         AttributeValue::S(backup_id.to_string()),
       ),
     ]);
 
     match self
       .client
       .get_item()
       .table_name(BACKUP_TABLE_NAME)
       .set_key(Some(item_key))
       .send()
       .await
       .map_err(|e| {
         error!("DynamoDB client failed to find backup item");
         Error::AwsSdk(e.into())
       })? {
       GetItemOutput {
         item: Some(item), ..
       } => {
-        let backup_item = parse_backup_item(item)?;
+        let backup_item = item.try_into()?;
         Ok(Some(backup_item))
       }
       _ => Ok(None),
     }
   }
 
   pub async fn find_last_backup_item(
     &self,
     user_id: &str,
   ) -> Result<Option<BackupItem>, Error> {
     let response = self
       .client
       .query()
       .table_name(BACKUP_TABLE_NAME)
       .index_name(BACKUP_TABLE_INDEX_USERID_CREATED)
       .key_condition_expression("#userID = :valueToMatch")
       .expression_attribute_names("#userID", BACKUP_TABLE_FIELD_USER_ID)
       .expression_attribute_values(
         ":valueToMatch",
         AttributeValue::S(user_id.to_string()),
       )
       .limit(1)
       .scan_index_forward(false)
       .send()
       .await
       .map_err(|e| {
         error!("DynamoDB client failed to find last backup");
         Error::AwsSdk(e.into())
       })?;
 
     match response.items.unwrap_or_default().pop() {
       Some(item) => {
-        let backup_item = parse_backup_item(item)?;
+        let backup_item = item.try_into()?;
         Ok(Some(backup_item))
       }
       None => Ok(None),
     }
   }
 
   pub async fn remove_backup_item(&self, backup_id: &str) -> Result<(), Error> {
     self
       .client
       .delete_item()
       .table_name(BACKUP_TABLE_NAME)
       .key(
         BACKUP_TABLE_FIELD_BACKUP_ID,
         AttributeValue::S(backup_id.to_string()),
       )
       .send()
       .await
       .map_err(|e| {
         error!("DynamoDB client failed to remove backup item");
         Error::AwsSdk(e.into())
       })?;
 
     Ok(())
   }
 
   // log item
   pub async fn put_log_item(&self, log_item: LogItem) -> Result<(), Error> {
     let item = HashMap::from([
       (
         LOG_TABLE_FIELD_BACKUP_ID.to_string(),
         AttributeValue::S(log_item.backup_id),
       ),
       (
         LOG_TABLE_FIELD_LOG_ID.to_string(),
         AttributeValue::S(log_item.log_id),
       ),
       (
         LOG_TABLE_FIELD_PERSISTED_IN_BLOB.to_string(),
         AttributeValue::Bool(log_item.persisted_in_blob),
       ),
       (
         LOG_TABLE_FIELD_VALUE.to_string(),
         AttributeValue::S(log_item.value),
       ),
       (
         LOG_TABLE_FIELD_DATA_HASH.to_string(),
         AttributeValue::S(log_item.data_hash),
       ),
       (
         LOG_TABLE_FIELD_ATTACHMENT_HOLDERS.to_string(),
         AttributeValue::S(log_item.attachment_holders),
       ),
     ]);
 
     self
       .client
       .put_item()
       .table_name(LOG_TABLE_NAME)
       .set_item(Some(item))
       .send()
       .await
       .map_err(|e| {
         error!("DynamoDB client failed to put log item");
         Error::AwsSdk(e.into())
       })?;
 
     Ok(())
   }
 
   pub async fn find_log_item(
     &self,
     backup_id: &str,
     log_id: &str,
   ) -> Result<Option<LogItem>, Error> {
     let item_key = HashMap::from([
       (
         LOG_TABLE_FIELD_BACKUP_ID.to_string(),
         AttributeValue::S(backup_id.to_string()),
       ),
       (
         LOG_TABLE_FIELD_LOG_ID.to_string(),
         AttributeValue::S(log_id.to_string()),
       ),
     ]);
 
     match self
       .client
       .get_item()
       .table_name(LOG_TABLE_NAME)
       .set_key(Some(item_key))
       .send()
       .await
       .map_err(|e| {
         error!("DynamoDB client failed to find log item");
         Error::AwsSdk(e.into())
       })? {
       GetItemOutput {
         item: Some(item), ..
       } => {
         let log_item = parse_log_item(item)?;
         Ok(Some(log_item))
       }
       _ => Ok(None),
     }
   }
 
   pub async fn find_log_items_for_backup(
     &self,
     backup_id: &str,
   ) -> Result<Vec<LogItem>, Error> {
     let response = self
       .client
       .query()
       .table_name(LOG_TABLE_NAME)
       .key_condition_expression("#backupID = :valueToMatch")
       .expression_attribute_names("#backupID", LOG_TABLE_FIELD_BACKUP_ID)
       .expression_attribute_values(
         ":valueToMatch",
         AttributeValue::S(backup_id.to_string()),
       )
       .send()
       .await
       .map_err(|e| {
         error!("DynamoDB client failed to find log items for backup");
         Error::AwsSdk(e.into())
       })?;
 
     if response.count == 0 {
       return Ok(Vec::new());
     }
 
     let mut results: Vec<LogItem> =
       Vec::with_capacity(response.count() as usize);
     for item in response.items.unwrap_or_default() {
       let log_item = parse_log_item(item)?;
       results.push(log_item);
     }
     Ok(results)
   }
 
   pub async fn remove_log_item(&self, log_id: &str) -> Result<(), Error> {
     self
       .client
       .delete_item()
       .table_name(LOG_TABLE_NAME)
       .key(
         LOG_TABLE_FIELD_LOG_ID,
         AttributeValue::S(log_id.to_string()),
       )
       .send()
       .await
       .map_err(|e| {
         error!("DynamoDB client failed to remove log item");
         Error::AwsSdk(e.into())
       })?;
 
     Ok(())
   }
 }
diff --git a/services/comm-services-lib/src/database.rs b/services/comm-services-lib/src/database.rs
index 8b0409ded..405df941a 100644
--- a/services/comm-services-lib/src/database.rs
+++ b/services/comm-services-lib/src/database.rs
@@ -1,597 +1,619 @@
 use aws_sdk_dynamodb::types::AttributeValue;
 use aws_sdk_dynamodb::Error as DynamoDBError;
 use chrono::{DateTime, Utc};
+use std::collections::HashSet;
 use std::fmt::{Display, Formatter};
 use std::num::ParseIntError;
 use std::str::FromStr;
 
 // # Useful type aliases
 
 // Rust exports `pub type` only into the so-called "type namespace", but in
 // order to use them e.g. with the `TryFromAttribute` trait, they also need
 // to be exported into the "value namespace" which is what `pub use` does.
 //
 // To overcome that, a dummy module is created and aliases are re-exported
 // with `pub use` construct
 mod aliases {
   use aws_sdk_dynamodb::types::AttributeValue;
   use std::collections::HashMap;
   pub type AttributeMap = HashMap<String, AttributeValue>;
 }
 pub use self::aliases::AttributeMap;
 
 // # Error handling
 
 #[derive(
   Debug, derive_more::Display, derive_more::From, derive_more::Error,
 )]
 pub enum Error {
   #[display(...)]
   AwsSdk(DynamoDBError),
   #[display(...)]
   Attribute(DBItemError),
   #[display(fmt = "Maximum retries exceeded")]
   MaxRetriesExceeded,
 }
 
 #[derive(Debug)]
 pub enum Value {
   AttributeValue(Option<AttributeValue>),
   String(String),
 }
 
 #[derive(Debug, derive_more::Error, derive_more::Constructor)]
 pub struct DBItemError {
   attribute_name: String,
   attribute_value: Value,
   attribute_error: DBItemAttributeError,
 }
 
 impl Display for DBItemError {
   fn fmt(&self, f: &mut Formatter) -> std::fmt::Result {
     match &self.attribute_error {
       DBItemAttributeError::Missing => {
         write!(f, "Attribute {} is missing", self.attribute_name)
       }
       DBItemAttributeError::IncorrectType => write!(
         f,
         "Value for attribute {} has incorrect type: {:?}",
         self.attribute_name, self.attribute_value
       ),
       error => write!(
         f,
         "Error regarding attribute {} with value {:?}: {}",
         self.attribute_name, self.attribute_value, error
       ),
     }
   }
 }
 
 #[derive(Debug, derive_more::Display, derive_more::Error)]
 pub enum DBItemAttributeError {
   #[display(...)]
   Missing,
   #[display(...)]
   IncorrectType,
   #[display(...)]
   TimestampOutOfRange,
   #[display(...)]
   InvalidTimestamp(chrono::ParseError),
   #[display(...)]
   InvalidNumberFormat(ParseIntError),
 }
 
 /// Conversion trait for [`AttributeValue`]
 ///
 /// Types implementing this trait are able to do the following:
 /// ```ignore
 /// use comm_services_lib::database::{TryFromAttribute, AttributeTryInto};
 ///
 /// let foo = SomeType::try_from_attr("MyAttribute", Some(attribute))?;
 ///
 /// // if `AttributeTryInto` is imported, also:
 /// let bar = Some(attribute).attr_try_into("MyAttribute")?;
 /// ```
 pub trait TryFromAttribute: Sized {
   fn try_from_attr(
     attribute_name: impl Into<String>,
     attribute: Option<AttributeValue>,
   ) -> Result<Self, DBItemError>;
 }
 
 /// Do NOT implement this trait directly. Implement [`TryFromAttribute`] instead
 pub trait AttributeTryInto<T> {
   fn attr_try_into(
     self,
     attribute_name: impl Into<String>,
   ) -> Result<T, DBItemError>;
 }
 // Automatic attr_try_into() for all attribute values
 // that have TryFromAttribute implemented
 impl<T: TryFromAttribute> AttributeTryInto<T> for Option<AttributeValue> {
   fn attr_try_into(
     self,
     attribute_name: impl Into<String>,
   ) -> Result<T, DBItemError> {
     T::try_from_attr(attribute_name, self)
   }
 }
 
 /// Helper trait for extracting attributes from a collection
 pub trait AttributeExtractor {
   /// Gets an attribute from the map and tries to convert it to the given type
   /// This method does not consume the raw attribute - it gets cloned
   /// See [`AttributeExtractor::take_attr`] for a non-cloning method
   fn get_attr<T: TryFromAttribute>(
     &self,
     attribute_name: &str,
   ) -> Result<T, DBItemError>;
   /// Takes an attribute from the map and tries to convert it to the given type
   /// This method consumes the raw attribute - it gets removed from the map
   /// See [`AttributeExtractor::get_attr`] for a non-mutating method
   fn take_attr<T: TryFromAttribute>(
     &mut self,
     attribute_name: &str,
   ) -> Result<T, DBItemError>;
 }
 impl AttributeExtractor for AttributeMap {
   fn get_attr<T: TryFromAttribute>(
     &self,
     attribute_name: &str,
   ) -> Result<T, DBItemError> {
     T::try_from_attr(attribute_name, self.get(attribute_name).cloned())
   }
   fn take_attr<T: TryFromAttribute>(
     &mut self,
     attribute_name: &str,
   ) -> Result<T, DBItemError> {
     T::try_from_attr(attribute_name, self.remove(attribute_name))
   }
 }
 
 impl TryFromAttribute for String {
   fn try_from_attr(
     attribute_name: impl Into<String>,
     attribute_value: Option<AttributeValue>,
   ) -> Result<Self, DBItemError> {
     match attribute_value {
       Some(AttributeValue::S(value)) => Ok(value),
       Some(_) => Err(DBItemError::new(
         attribute_name.into(),
         Value::AttributeValue(attribute_value),
         DBItemAttributeError::IncorrectType,
       )),
       None => Err(DBItemError::new(
         attribute_name.into(),
         Value::AttributeValue(attribute_value),
         DBItemAttributeError::Missing,
       )),
     }
   }
 }
 
 impl TryFromAttribute for bool {
   fn try_from_attr(
     attribute_name: impl Into<String>,
     attribute_value: Option<AttributeValue>,
   ) -> Result<Self, DBItemError> {
     match attribute_value {
       Some(AttributeValue::Bool(value)) => Ok(value),
       Some(_) => Err(DBItemError::new(
         attribute_name.into(),
         Value::AttributeValue(attribute_value),
         DBItemAttributeError::IncorrectType,
       )),
       None => Err(DBItemError::new(
         attribute_name.into(),
         Value::AttributeValue(attribute_value),
         DBItemAttributeError::Missing,
       )),
     }
   }
 }
 
 impl TryFromAttribute for DateTime<Utc> {
   fn try_from_attr(
     attribute_name: impl Into<String>,
     attribute: Option<AttributeValue>,
   ) -> Result<Self, DBItemError> {
     match &attribute {
       Some(AttributeValue::S(datetime)) => datetime.parse().map_err(|e| {
         DBItemError::new(
           attribute_name.into(),
           Value::AttributeValue(attribute),
           DBItemAttributeError::InvalidTimestamp(e),
         )
       }),
       Some(_) => Err(DBItemError::new(
         attribute_name.into(),
         Value::AttributeValue(attribute),
         DBItemAttributeError::IncorrectType,
       )),
       None => Err(DBItemError::new(
         attribute_name.into(),
         Value::AttributeValue(attribute),
         DBItemAttributeError::Missing,
       )),
     }
   }
 }
 
 impl TryFromAttribute for AttributeMap {
   fn try_from_attr(
     attribute_name: impl Into<String>,
     attribute_value: Option<AttributeValue>,
   ) -> Result<Self, DBItemError> {
     match attribute_value {
       Some(AttributeValue::M(map)) => Ok(map),
       Some(_) => Err(DBItemError::new(
         attribute_name.into(),
         Value::AttributeValue(attribute_value),
         DBItemAttributeError::IncorrectType,
       )),
       None => Err(DBItemError::new(
         attribute_name.into(),
         Value::AttributeValue(attribute_value),
         DBItemAttributeError::Missing,
       )),
     }
   }
 }
 
 impl TryFromAttribute for Vec<u8> {
   fn try_from_attr(
     attribute_name: impl Into<String>,
     attribute_value: Option<AttributeValue>,
   ) -> Result<Self, DBItemError> {
     match attribute_value {
       Some(AttributeValue::B(data)) => Ok(data.into_inner()),
       Some(_) => Err(DBItemError::new(
         attribute_name.into(),
         Value::AttributeValue(attribute_value),
         DBItemAttributeError::IncorrectType,
       )),
       None => Err(DBItemError::new(
         attribute_name.into(),
         Value::AttributeValue(attribute_value),
         DBItemAttributeError::Missing,
       )),
     }
   }
 }
 
+impl TryFromAttribute for HashSet<String> {
+  fn try_from_attr(
+    attribute_name: impl Into<String>,
+    attribute_value: Option<AttributeValue>,
+  ) -> Result<Self, DBItemError> {
+    match attribute_value {
+      Some(AttributeValue::Ss(set)) => Ok(set.into_iter().collect()),
+      Some(_) => Err(DBItemError::new(
+        attribute_name.into(),
+        Value::AttributeValue(attribute_value),
+        DBItemAttributeError::IncorrectType,
+      )),
+      None => Err(DBItemError::new(
+        attribute_name.into(),
+        Value::AttributeValue(attribute_value),
+        DBItemAttributeError::Missing,
+      )),
+    }
+  }
+}
+
 #[deprecated = "Use `String::try_from_attr()` instead"]
 pub fn parse_string_attribute(
   attribute_name: impl Into<String>,
   attribute_value: Option<AttributeValue>,
 ) -> Result<String, DBItemError> {
   String::try_from_attr(attribute_name, attribute_value)
 }
 
 #[deprecated = "Use `bool::try_from_attr()` instead"]
 pub fn parse_bool_attribute(
   attribute_name: impl Into<String>,
   attribute_value: Option<AttributeValue>,
 ) -> Result<bool, DBItemError> {
   bool::try_from_attr(attribute_name, attribute_value)
 }
 
 #[deprecated = "Use `DateTime::<Utc>::try_from_attr()` instead"]
 pub fn parse_datetime_attribute(
   attribute_name: impl Into<String>,
   attribute_value: Option<AttributeValue>,
 ) -> Result<DateTime<Utc>, DBItemError> {
   DateTime::<Utc>::try_from_attr(attribute_name, attribute_value)
 }
 
 #[deprecated = "Use `AttributeMap::try_from_attr()` instead"]
 pub fn parse_map_attribute(
   attribute_name: impl Into<String>,
   attribute_value: Option<AttributeValue>,
 ) -> Result<AttributeMap, DBItemError> {
   attribute_value.attr_try_into(attribute_name)
 }
 
 pub fn parse_int_attribute<T>(
   attribute_name: impl Into<String>,
   attribute_value: Option<AttributeValue>,
 ) -> Result<T, DBItemError>
 where
   T: FromStr<Err = ParseIntError>,
 {
   match &attribute_value {
     Some(AttributeValue::N(numeric_str)) => {
       parse_integer(attribute_name, numeric_str)
     }
     Some(_) => Err(DBItemError::new(
       attribute_name.into(),
       Value::AttributeValue(attribute_value),
       DBItemAttributeError::IncorrectType,
     )),
     None => Err(DBItemError::new(
       attribute_name.into(),
       Value::AttributeValue(attribute_value),
       DBItemAttributeError::Missing,
     )),
   }
 }
 
 /// Parses the UTC timestamp in milliseconds from a DynamoDB numeric attribute
 pub fn parse_timestamp_attribute(
   attribute_name: impl Into<String>,
   attribute_value: Option<AttributeValue>,
 ) -> Result<DateTime<Utc>, DBItemError> {
   let attribute_name: String = attribute_name.into();
   let timestamp = parse_int_attribute::<i64>(
     attribute_name.clone(),
     attribute_value.clone(),
   )?;
   let naive_datetime = chrono::NaiveDateTime::from_timestamp_millis(timestamp)
     .ok_or_else(|| {
       DBItemError::new(
         attribute_name,
         Value::AttributeValue(attribute_value),
         DBItemAttributeError::TimestampOutOfRange,
       )
     })?;
   Ok(DateTime::from_utc(naive_datetime, Utc))
 }
 
 pub fn parse_integer<T>(
   attribute_name: impl Into<String>,
   attribute_value: &str,
 ) -> Result<T, DBItemError>
 where
   T: FromStr<Err = ParseIntError>,
 {
   attribute_value.parse::<T>().map_err(|e| {
     DBItemError::new(
       attribute_name.into(),
       Value::String(attribute_value.into()),
       DBItemAttributeError::InvalidNumberFormat(e),
     )
   })
 }
 
 pub mod batch_operations {
   use aws_sdk_dynamodb::{
     error::SdkError, operation::batch_write_item::BatchWriteItemError,
     types::WriteRequest,
   };
   use rand::Rng;
   use std::time::Duration;
   use tracing::{debug, trace};
 
   /// DynamoDB hard limit for single BatchWriteItem request
   const SINGLE_BATCH_ITEM_LIMIT: usize = 25;
 
   /// Exponential backoff configuration for batch write operation
   #[derive(derive_more::Constructor, Debug)]
   pub struct ExponentialBackoffConfig {
     /// Maximum retry attempts before the function fails.
     /// Set this to 0 to disable exponential backoff.
     /// Defaults to **8**.
     pub max_attempts: u32,
     /// Base wait duration before retry. Defaults to **25ms**.
     /// It is doubled with each attempt: 25ms, 50, 100, 200...
     pub base_duration: Duration,
     /// Jitter factor for retry delay. Factor 0.5 for 100ms delay
     /// means that wait time will be between 50ms and 150ms.
     /// The value must be in range 0.0 - 1.0. It will be clamped
     /// if out of these bounds. Defaults to **0.3**
     pub jitter_factor: f32,
     /// Retry on [`ProvisionedThroughputExceededException`].
     /// Defaults to **true**.
     ///
     /// [`ProvisionedThroughputExceededException`]: aws_sdk_dynamodb::Error::ProvisionedThroughputExceededException
     pub retry_on_provisioned_capacity_exceeded: bool,
   }
 
   impl Default for ExponentialBackoffConfig {
     fn default() -> Self {
       ExponentialBackoffConfig {
         max_attempts: 8,
         base_duration: Duration::from_millis(25),
         jitter_factor: 0.3,
         retry_on_provisioned_capacity_exceeded: true,
       }
     }
   }
 
   impl ExponentialBackoffConfig {
     fn new_counter(&self) -> ExponentialBackoffHelper {
       ExponentialBackoffHelper::new(self)
     }
     fn backoff_enabled(&self) -> bool {
       self.max_attempts > 0
     }
     fn should_retry_on_capacity_exceeded(&self) -> bool {
       self.backoff_enabled() && self.retry_on_provisioned_capacity_exceeded
     }
   }
 
   /// Performs a single DynamoDB table batch write operation. If the batch
   /// contains more than 25 items, it is split into chunks.
   ///
   /// The function uses exponential backoff retries when AWS throttles
   /// the request or maximum provisioned capacity is exceeded
   #[tracing::instrument(name = "batch_write", skip(ddb, requests, config))]
   pub async fn batch_write(
     ddb: &aws_sdk_dynamodb::Client,
     table_name: &str,
     mut requests: Vec<WriteRequest>,
     config: ExponentialBackoffConfig,
   ) -> Result<(), super::Error> {
     tracing::debug!(
       ?config,
       "Starting batch write operation of {} items...",
       requests.len()
     );
 
     let mut exponential_backoff = config.new_counter();
     let mut backup = Vec::with_capacity(SINGLE_BATCH_ITEM_LIMIT);
 
     loop {
       let items_to_drain =
         std::cmp::min(requests.len(), SINGLE_BATCH_ITEM_LIMIT);
       let chunk = requests.drain(..items_to_drain).collect::<Vec<_>>();
       if chunk.is_empty() {
         // No more items
         tracing::trace!("No more items to process. Exiting");
         break;
       }
 
       // we don't need the backup when we don't retry
       if config.should_retry_on_capacity_exceeded() {
         chunk.clone_into(&mut backup);
       }
 
       tracing::trace!("Attempting to write chunk of {} items...", chunk.len());
       let result = ddb
         .batch_write_item()
         .request_items(table_name, chunk)
         .send()
         .await;
 
       match result {
         Ok(output) => {
           if let Some(mut items) = output.unprocessed_items {
             let requests_to_retry =
               items.remove(table_name).unwrap_or_default();
             if requests_to_retry.is_empty() {
               tracing::trace!("Chunk written successfully. Continuing.");
               exponential_backoff.reset();
               continue;
             }
 
             exponential_backoff.sleep_and_retry().await?;
             tracing::debug!(
               "Some items failed. Retrying {} requests",
               requests_to_retry.len()
             );
             requests.extend(requests_to_retry);
           } else {
             tracing::trace!("Unprocessed items was None");
           }
         }
         Err(error) => {
           if !is_provisioned_capacity_exceeded(&error) {
             tracing::error!("BatchWriteItem failed: {0:?} - {0}", error);
             return Err(super::Error::AwsSdk(error.into()));
           }
 
           tracing::warn!("Provisioned capacity exceeded!");
           if !config.retry_on_provisioned_capacity_exceeded {
             return Err(super::Error::AwsSdk(error.into()));
           }
           exponential_backoff.sleep_and_retry().await?;
           requests.append(&mut backup);
           trace!("Retrying now...");
         }
       };
     }
 
     debug!("Batch write completed.");
     Ok(())
   }
 
   /// internal helper struct
   struct ExponentialBackoffHelper<'cfg> {
     config: &'cfg ExponentialBackoffConfig,
     attempt: u32,
   }
 
   impl<'cfg> ExponentialBackoffHelper<'cfg> {
     fn new(config: &'cfg ExponentialBackoffConfig) -> Self {
       ExponentialBackoffHelper { config, attempt: 0 }
     }
 
     /// reset counter after successfull operation
     fn reset(&mut self) {
       self.attempt = 0;
     }
 
     /// increase counter and sleep in case of failure
     async fn sleep_and_retry(&mut self) -> Result<(), super::Error> {
       let jitter_factor = 1f32.min(0f32.max(self.config.jitter_factor));
       let random_multiplier =
         1.0 + rand::thread_rng().gen_range(-jitter_factor..=jitter_factor);
       let backoff_multiplier = 2u32.pow(self.attempt);
       let base_duration = self.config.base_duration * backoff_multiplier;
       let sleep_duration = base_duration.mul_f32(random_multiplier);
 
       self.attempt += 1;
       if self.attempt > self.config.max_attempts {
         tracing::warn!("Retry limit exceeded!");
         return Err(super::Error::MaxRetriesExceeded);
       }
       tracing::debug!(
         attempt = self.attempt,
         "Batch failed. Sleeping for {}ms before retrying...",
         sleep_duration.as_millis()
       );
       tokio::time::sleep(sleep_duration).await;
       Ok(())
     }
   }
 
   /// Check if transaction failed due to
   /// `ProvisionedThroughputExceededException` exception
   fn is_provisioned_capacity_exceeded(
     err: &SdkError<BatchWriteItemError>,
   ) -> bool {
     let SdkError::ServiceError(service_error) = err else {
       return false;
     };
     matches!(
       service_error.err(),
       BatchWriteItemError::ProvisionedThroughputExceededException(_)
     )
   }
 }
 
 #[cfg(test)]
 mod tests {
   use super::*;
 
   #[test]
   fn test_parse_integer() {
     assert!(parse_integer::<i32>("some_attr", "123").is_ok());
     assert!(parse_integer::<i32>("negative", "-123").is_ok());
 
     assert!(parse_integer::<i32>("float", "3.14").is_err());
     assert!(parse_integer::<i32>("NaN", "foo").is_err());
 
     assert!(parse_integer::<u32>("negative_uint", "-123").is_err());
     assert!(parse_integer::<u8>("too_large", "65536").is_err());
   }
 
   #[test]
   fn test_parse_timestamp() {
     let timestamp = Utc::now().timestamp_millis();
     let attr = AttributeValue::N(timestamp.to_string());
 
     let parsed_timestamp = parse_timestamp_attribute("some_attr", Some(attr));
 
     assert!(parsed_timestamp.is_ok());
     assert_eq!(parsed_timestamp.unwrap().timestamp_millis(), timestamp);
   }
 
   #[test]
   fn test_parse_invalid_timestamp() {
     let attr = AttributeValue::N("foo".to_string());
     let parsed_timestamp = parse_timestamp_attribute("some_attr", Some(attr));
     assert!(parsed_timestamp.is_err());
   }
 
   #[test]
   fn test_parse_timestamp_out_of_range() {
     let attr = AttributeValue::N(i64::MAX.to_string());
     let parsed_timestamp = parse_timestamp_attribute("some_attr", Some(attr));
     assert!(parsed_timestamp.is_err());
     assert!(matches!(
       parsed_timestamp.unwrap_err().attribute_error,
       DBItemAttributeError::TimestampOutOfRange
     ));
   }
 }