diff --git a/services/identity/src/database/device_list.rs b/services/identity/src/database/device_list.rs
index d3644b671..04fa117cc 100644
--- a/services/identity/src/database/device_list.rs
+++ b/services/identity/src/database/device_list.rs
@@ -1,461 +1,620 @@
 // TODO: get rid of this
 #![allow(dead_code)]
 
 use std::collections::HashMap;
 
 use aws_sdk_dynamodb::{
-  client::fluent_builders::Query, model::AttributeValue, output::GetItemOutput,
+  client::fluent_builders::Query,
+  error::TransactionCanceledException,
+  model::{AttributeValue, Put, TransactWriteItem, Update},
+  output::GetItemOutput,
 };
 use chrono::{DateTime, Utc};
 use tracing::{error, warn};
 
 use crate::{
   constants::{
     devices_table::{self, *},
     USERS_TABLE, USERS_TABLE_DEVICELIST_TIMESTAMP_ATTRIBUTE_NAME,
     USERS_TABLE_PARTITION_KEY,
   },
   database::parse_string_attribute,
   ddb_utils::AttributesOptionExt,
-  error::{DBItemAttributeError, DBItemError, Error, FromAttributeValue},
+  error::{
+    DBItemAttributeError, DBItemError, DeviceListError, Error,
+    FromAttributeValue,
+  },
   grpc_services::protos::unauth::DeviceType,
 };
 
 use super::{parse_date_time_attribute, DatabaseClient};
 
 type RawAttributes = HashMap<String, AttributeValue>;
 
 #[derive(Clone, Debug)]
 pub enum DevicesTableRow {
   Device(DeviceRow),
   DeviceList(DeviceListRow),
 }
 
 #[derive(Clone, Debug)]
 pub struct DeviceRow {
   pub user_id: String,
   pub device_id: String,
   pub device_type: DeviceType,
   pub device_key_info: IdentityKeyInfo,
   pub content_prekey: PreKey,
   pub notif_prekey: PreKey,
 }
 
 #[derive(Clone, Debug)]
 pub struct DeviceListRow {
   pub user_id: String,
   pub timestamp: DateTime<Utc>,
   pub device_ids: Vec<String>,
 }
 
 #[derive(Clone, Debug)]
 pub struct IdentityKeyInfo {
   pub key_payload: String,
   pub key_payload_signature: String,
   pub social_proof: Option<String>,
 }
 
 #[derive(Clone, Debug)]
 pub struct PreKey {
   pub pre_key: String,
   pub pre_key_signature: String,
 }
 
+impl DeviceListRow {
+  /// Generates new device list row from given devices
+  fn new(user_id: impl Into<String>, device_ids: Vec<String>) -> Self {
+    Self {
+      user_id: user_id.into(),
+      device_ids,
+      timestamp: Utc::now(),
+    }
+  }
+}
+
 // helper structs for converting to/from attribute values for sort key (a.k.a itemID)
 struct DeviceIDAttribute(String);
 struct DeviceListKeyAttribute(DateTime<Utc>);
 
 impl From<DeviceIDAttribute> for AttributeValue {
   fn from(value: DeviceIDAttribute) -> Self {
     AttributeValue::S(format!("{DEVICE_ITEM_KEY_PREFIX}{}", value.0))
   }
 }
 
 impl From<DeviceListKeyAttribute> for AttributeValue {
   fn from(value: DeviceListKeyAttribute) -> Self {
     AttributeValue::S(format!(
       "{DEVICE_LIST_KEY_PREFIX}{}",
       value.0.to_rfc3339()
     ))
   }
 }
 
 impl TryFrom<Option<AttributeValue>> for DeviceIDAttribute {
   type Error = DBItemError;
   fn try_from(value: Option<AttributeValue>) -> Result<Self, Self::Error> {
     let item_id = parse_string_attribute(ATTR_ITEM_ID, value)?;
 
     // remove the device- prefix
     let device_id = item_id
       .strip_prefix(DEVICE_ITEM_KEY_PREFIX)
       .ok_or_else(|| DBItemError {
         attribute_name: ATTR_ITEM_ID.to_string(),
         attribute_value: Some(AttributeValue::S(item_id.clone())),
         attribute_error: DBItemAttributeError::InvalidValue,
       })?
       .to_string();
 
     Ok(Self(device_id))
   }
 }
 
 impl TryFrom<Option<AttributeValue>> for DeviceListKeyAttribute {
   type Error = DBItemError;
   fn try_from(value: Option<AttributeValue>) -> Result<Self, Self::Error> {
     let item_id = parse_string_attribute(ATTR_ITEM_ID, value)?;
 
     // remove the device-list- prefix, then parse the timestamp
     let timestamp: DateTime<Utc> = item_id
       .strip_prefix(DEVICE_LIST_KEY_PREFIX)
       .ok_or_else(|| DBItemError {
         attribute_name: ATTR_ITEM_ID.to_string(),
         attribute_value: Some(AttributeValue::S(item_id.clone())),
         attribute_error: DBItemAttributeError::InvalidValue,
       })
       .and_then(|s| {
         s.parse().map_err(|e| {
           DBItemError::new(
             ATTR_ITEM_ID.to_string(),
             Some(AttributeValue::S(item_id.clone())),
             DBItemAttributeError::InvalidTimestamp(e),
           )
         })
       })?;
 
     Ok(Self(timestamp))
   }
 }
 
 impl TryFrom<RawAttributes> for DeviceRow {
   type Error = DBItemError;
 
   fn try_from(mut attrs: RawAttributes) -> Result<Self, Self::Error> {
     let user_id =
       parse_string_attribute(ATTR_USER_ID, attrs.remove(ATTR_USER_ID))?;
     let DeviceIDAttribute(device_id) = attrs.remove(ATTR_ITEM_ID).try_into()?;
 
     let raw_device_type =
       parse_string_attribute(ATTR_DEVICE_TYPE, attrs.remove(ATTR_DEVICE_TYPE))?;
     let device_type =
       DeviceType::from_str_name(&raw_device_type).ok_or_else(|| {
         DBItemError::new(
           ATTR_DEVICE_TYPE.to_string(),
           Some(AttributeValue::S(raw_device_type)),
           DBItemAttributeError::InvalidValue,
         )
       })?;
 
     let device_key_info = attrs
       .remove(ATTR_DEVICE_KEY_INFO)
       .ok_or_missing(ATTR_DEVICE_KEY_INFO)?
       .to_hashmap(ATTR_DEVICE_KEY_INFO)
       .cloned()
       .and_then(IdentityKeyInfo::try_from)?;
 
     let content_prekey = attrs
       .remove(ATTR_CONTENT_PREKEY)
       .ok_or_missing(ATTR_CONTENT_PREKEY)?
       .to_hashmap(ATTR_CONTENT_PREKEY)
       .cloned()
       .and_then(PreKey::try_from)?;
 
     let notif_prekey = attrs
       .remove(ATTR_NOTIF_PREKEY)
       .ok_or_missing(ATTR_NOTIF_PREKEY)?
       .to_hashmap(ATTR_NOTIF_PREKEY)
       .cloned()
       .and_then(PreKey::try_from)?;
 
     Ok(Self {
       user_id,
       device_id,
       device_type,
       device_key_info,
       content_prekey,
       notif_prekey,
     })
   }
 }
 
 impl From<DeviceRow> for RawAttributes {
   fn from(value: DeviceRow) -> Self {
     HashMap::from([
       (ATTR_USER_ID.to_string(), AttributeValue::S(value.user_id)),
       (
         ATTR_ITEM_ID.to_string(),
         DeviceIDAttribute(value.device_id).into(),
       ),
       (
         ATTR_DEVICE_TYPE.to_string(),
         AttributeValue::S(value.device_type.as_str_name().to_string()),
       ),
       (
         ATTR_DEVICE_KEY_INFO.to_string(),
         value.device_key_info.into(),
       ),
       (ATTR_CONTENT_PREKEY.to_string(), value.content_prekey.into()),
       (ATTR_NOTIF_PREKEY.to_string(), value.notif_prekey.into()),
     ])
   }
 }
 
 impl From<IdentityKeyInfo> for AttributeValue {
   fn from(value: IdentityKeyInfo) -> Self {
     let mut attrs = HashMap::from([
       (
         ATTR_KEY_PAYLOAD.to_string(),
         AttributeValue::S(value.key_payload),
       ),
       (
         ATTR_KEY_PAYLOAD_SIGNATURE.to_string(),
         AttributeValue::S(value.key_payload_signature),
       ),
     ]);
     if let Some(social_proof) = value.social_proof {
       attrs.insert(
         ATTR_SOCIAL_PROOF.to_string(),
         AttributeValue::S(social_proof),
       );
     }
     AttributeValue::M(attrs)
   }
 }
 
 impl TryFrom<RawAttributes> for IdentityKeyInfo {
   type Error = DBItemError;
   fn try_from(mut attrs: RawAttributes) -> Result<Self, Self::Error> {
     let key_payload =
       parse_string_attribute(ATTR_KEY_PAYLOAD, attrs.remove(ATTR_KEY_PAYLOAD))?;
     let key_payload_signature = parse_string_attribute(
       ATTR_KEY_PAYLOAD_SIGNATURE,
       attrs.remove(ATTR_KEY_PAYLOAD_SIGNATURE),
     )?;
     // social proof is optional
     let social_proof = attrs
       .remove(ATTR_SOCIAL_PROOF)
       .map(|attr| attr.to_string(ATTR_SOCIAL_PROOF).cloned())
       .transpose()?;
 
     Ok(Self {
       key_payload,
       key_payload_signature,
       social_proof,
     })
   }
 }
 
 impl From<PreKey> for AttributeValue {
   fn from(value: PreKey) -> Self {
     let attrs = HashMap::from([
       (ATTR_PREKEY.to_string(), AttributeValue::S(value.pre_key)),
       (
         ATTR_PREKEY_SIGNATURE.to_string(),
         AttributeValue::S(value.pre_key_signature),
       ),
     ]);
     AttributeValue::M(attrs)
   }
 }
 
 impl TryFrom<RawAttributes> for PreKey {
   type Error = DBItemError;
   fn try_from(mut attrs: RawAttributes) -> Result<Self, Self::Error> {
     let pre_key =
       parse_string_attribute(ATTR_PREKEY, attrs.remove(ATTR_PREKEY))?;
     let pre_key_signature = parse_string_attribute(
       ATTR_PREKEY_SIGNATURE,
       attrs.remove(ATTR_PREKEY_SIGNATURE),
     )?;
     Ok(Self {
       pre_key,
       pre_key_signature,
     })
   }
 }
 
 impl TryFrom<RawAttributes> for DeviceListRow {
   type Error = DBItemError;
 
   fn try_from(mut attrs: RawAttributes) -> Result<Self, Self::Error> {
     let user_id =
       parse_string_attribute(ATTR_USER_ID, attrs.remove(ATTR_USER_ID))?;
     let DeviceListKeyAttribute(timestamp) =
       attrs.remove(ATTR_ITEM_ID).try_into()?;
 
     // validate timestamps are in sync
     let timestamps_match = attrs
       .remove(ATTR_TIMESTAMP)
       .and_then(|attr| attr.as_n().ok().cloned())
       .and_then(|val| val.parse::<i64>().ok())
       .filter(|val| *val == timestamp.timestamp_millis())
       .is_some();
     if !timestamps_match {
       warn!(
         "DeviceList timestamp mismatch for (userID={}, itemID={})",
         &user_id,
         timestamp.to_rfc3339()
       );
     }
 
     // this should be a list of strings
     let device_ids = attrs
       .remove(ATTR_DEVICE_IDS)
       .ok_or_else(|| {
         DBItemError::new(
           ATTR_DEVICE_IDS.to_string(),
           None,
           DBItemAttributeError::Missing,
         )
       })?
       .to_vec(ATTR_DEVICE_IDS)?
       .iter()
       .map(|v| v.to_string("device_ids[?]").cloned())
       .collect::<Result<Vec<String>, DBItemError>>()?;
 
     Ok(Self {
       user_id,
       timestamp,
       device_ids,
     })
   }
 }
 
 impl From<DeviceListRow> for RawAttributes {
   fn from(device_list: DeviceListRow) -> Self {
     let mut attrs = HashMap::new();
     attrs.insert(
       ATTR_USER_ID.to_string(),
       AttributeValue::S(device_list.user_id.clone()),
     );
     attrs.insert(
       ATTR_ITEM_ID.to_string(),
       DeviceListKeyAttribute(device_list.timestamp).into(),
     );
     attrs.insert(
       ATTR_TIMESTAMP.to_string(),
       AttributeValue::N(device_list.timestamp.timestamp_millis().to_string()),
     );
     attrs.insert(
       ATTR_DEVICE_IDS.to_string(),
       AttributeValue::L(
         device_list
           .device_ids
           .into_iter()
           .map(AttributeValue::S)
           .collect(),
       ),
     );
     attrs
   }
 }
 
 impl DatabaseClient {
   /// Retrieves user's current devices and their full data
   pub async fn get_current_devices(
     &self,
     user_id: impl Into<String>,
   ) -> Result<Vec<DeviceRow>, Error> {
     let response =
       query_rows_with_prefix(self, user_id, DEVICE_ITEM_KEY_PREFIX)
         .send()
         .await
         .map_err(|e| {
           error!("Failed to get current devices: {:?}", e);
           Error::AwsSdk(e.into())
         })?;
 
     let Some(rows) = response.items else {
       return Ok(Vec::new());
     };
 
     rows
       .into_iter()
       .map(DeviceRow::try_from)
       .collect::<Result<Vec<DeviceRow>, DBItemError>>()
       .map_err(Error::from)
   }
 
   /// Checks if given device exists on user's current device list
   pub async fn device_exists(
     &self,
     user_id: impl Into<String>,
     device_id: impl Into<String>,
   ) -> Result<bool, Error> {
     let GetItemOutput { item, .. } = self
       .client
       .get_item()
       .table_name(devices_table::NAME)
       .key(ATTR_USER_ID, AttributeValue::S(user_id.into()))
       .key(ATTR_ITEM_ID, DeviceIDAttribute(device_id.into()).into())
       // only fetch the primary key, we don't need the rest
       .projection_expression(format!("{ATTR_USER_ID}, {ATTR_ITEM_ID}"))
       .send()
       .await
       .map_err(|e| {
         error!("Failed to check if device exists: {:?}", e);
         Error::AwsSdk(e.into())
       })?;
 
     Ok(item.is_some())
   }
+
+  pub async fn get_current_device_list(
+    &self,
+    user_id: impl Into<String>,
+  ) -> Result<Option<DeviceListRow>, Error> {
+    self
+      .client
+      .query()
+      .table_name(devices_table::NAME)
+      .index_name(devices_table::TIMESTAMP_INDEX_NAME)
+      .consistent_read(true)
+      .key_condition_expression("#user_id = :user_id")
+      // sort descending
+      .scan_index_forward(false)
+      .expression_attribute_names("#user_id", ATTR_USER_ID)
+      .expression_attribute_values(
+        ":user_id",
+        AttributeValue::S(user_id.into()),
+      )
+      .limit(1)
+      .send()
+      .await
+      .map_err(|e| {
+        error!("Failed to query device list updates by index: {:?}", e);
+        Error::AwsSdk(e.into())
+      })?
+      .items
+      .and_then(|mut items| items.pop())
+      .map(DeviceListRow::try_from)
+      .transpose()
+      .map_err(Error::from)
+  }
+
+  /// Performs a transactional update of the device list for the user. Afterwards
+  /// generates a new device list and updates the timestamp in the users table.
+  /// This is done in a transaction. Operation fails if the device list has been
+  /// updated concurrently (timestamp mismatch).
+  async fn transact_update_devicelist(
+    &self,
+    user_id: &str,
+    // The closure performing a transactional update of the device list. It receives a mutable
+    // reference to the current device list. The closure should return a transactional DDB
+    // operation to be performed when updating the device list.
+    action: impl FnOnce(&mut Vec<String>) -> Result<TransactWriteItem, Error>,
+  ) -> Result<(), Error> {
+    let previous_timestamp =
+      get_current_devicelist_timestamp(self, user_id).await?;
+    let mut device_ids = self
+      .get_current_device_list(user_id)
+      .await?
+      .map(|device_list| device_list.device_ids)
+      .unwrap_or_default();
+
+    // Perform the update action, then generate new device list
+    let operation = action(&mut device_ids)?;
+    let new_device_list = DeviceListRow::new(user_id, device_ids);
+
+    // Update timestamp in users table
+    let timestamp_update_operation = device_list_timestamp_update_operation(
+      user_id,
+      previous_timestamp,
+      new_device_list.timestamp,
+    );
+
+    // Put updated device list (a new version)
+    let put_device_list = Put::builder()
+      .table_name(devices_table::NAME)
+      .set_item(Some(new_device_list.into()))
+      .condition_expression(
+        "attribute_not_exists(#user_id) AND attribute_not_exists(#item_id)",
+      )
+      .expression_attribute_names("#user_id", ATTR_USER_ID)
+      .expression_attribute_names("#item_id", ATTR_ITEM_ID)
+      .build();
+    let put_device_list_operation =
+      TransactWriteItem::builder().put(put_device_list).build();
+
+    self
+      .client
+      .transact_write_items()
+      .transact_items(operation)
+      .transact_items(put_device_list_operation)
+      .transact_items(timestamp_update_operation)
+      .send()
+      .await
+      .map_err(|e| match aws_sdk_dynamodb::Error::from(e) {
+        aws_sdk_dynamodb::Error::TransactionCanceledException(
+          TransactionCanceledException {
+            cancellation_reasons: Some(reasons),
+            ..
+          },
+        ) if reasons
+          .iter()
+          .any(|reason| reason.code() == Some("ConditionalCheckFailed")) =>
+        {
+          Error::DeviceList(DeviceListError::ConcurrentUpdateError)
+        }
+        other => {
+          error!("Device list update transaction failed: {:?}", other);
+          Error::AwsSdk(other)
+        }
+      })?;
+
+    Ok(())
+  }
 }
 
 /// Gets timestamp of user's current device list. Returns None if the user
 /// doesn't have a device list yet. Storing the timestamp in the users table is
 /// required for consistency. It's used as a condition when updating the device
 /// list.
 async fn get_current_devicelist_timestamp(
   db: &crate::database::DatabaseClient,
   user_id: impl Into<String>,
 ) -> Result<Option<DateTime<Utc>>, Error> {
   let response = db
     .client
     .get_item()
     .table_name(USERS_TABLE)
     .key(USERS_TABLE_PARTITION_KEY, AttributeValue::S(user_id.into()))
     .projection_expression(USERS_TABLE_DEVICELIST_TIMESTAMP_ATTRIBUTE_NAME)
     .send()
     .await
     .map_err(|e| {
       error!("Failed to get user's device list timestamp: {:?}", e);
       Error::AwsSdk(e.into())
     })?;
 
   let mut user_item = response.item.unwrap_or_default();
   let raw_datetime =
     user_item.remove(USERS_TABLE_DEVICELIST_TIMESTAMP_ATTRIBUTE_NAME);
 
   // existing records will not have this field when
   // updating device list for the first time
   if raw_datetime.is_none() {
     return Ok(None);
   }
 
   let timestamp = parse_date_time_attribute(
     USERS_TABLE_DEVICELIST_TIMESTAMP_ATTRIBUTE_NAME,
     raw_datetime,
   )?;
   Ok(Some(timestamp))
 }
 
+/// Generates update expression for current device list timestamp in users table.
+/// The previous timestamp is used as a condition to ensure that the value hasn't changed
+/// since we got it. This avoids race conditions when updating the device list.
+fn device_list_timestamp_update_operation(
+  user_id: impl Into<String>,
+  previous_timestamp: Option<DateTime<Utc>>,
+  new_timestamp: DateTime<Utc>,
+) -> TransactWriteItem {
+  let update_builder = match previous_timestamp {
+    Some(previous_timestamp) => Update::builder()
+      .condition_expression("#device_list_timestamp = :previous_timestamp")
+      .expression_attribute_values(
+        ":previous_timestamp",
+        AttributeValue::S(previous_timestamp.to_rfc3339()),
+      ),
+    // If there's no previous timestamp, the attribute shouldn't exist yet
+    None => Update::builder()
+      .condition_expression("attribute_not_exists(#device_list_timestamp)"),
+  };
+
+  let update = update_builder
+    .table_name(USERS_TABLE)
+    .key(USERS_TABLE_PARTITION_KEY, AttributeValue::S(user_id.into()))
+    .update_expression("SET #device_list_timestamp = :new_timestamp")
+    .expression_attribute_names(
+      "#device_list_timestamp",
+      USERS_TABLE_DEVICELIST_TIMESTAMP_ATTRIBUTE_NAME,
+    )
+    .expression_attribute_values(
+      ":new_timestamp",
+      AttributeValue::S(new_timestamp.to_rfc3339()),
+    )
+    .build();
+
+  TransactWriteItem::builder().update(update).build()
+}
+
 /// Helper function to query rows by given sort key prefix
 fn query_rows_with_prefix(
   db: &crate::database::DatabaseClient,
   user_id: impl Into<String>,
   prefix: &'static str,
 ) -> Query {
   db.client
     .query()
     .table_name(devices_table::NAME)
     .key_condition_expression(
       "#user_id = :user_id AND begins_with(#item_id, :device_prefix)",
     )
     .expression_attribute_names("#user_id", ATTR_USER_ID)
     .expression_attribute_names("#item_id", ATTR_ITEM_ID)
     .expression_attribute_values(":user_id", AttributeValue::S(user_id.into()))
     .expression_attribute_values(
       ":device_prefix",
       AttributeValue::S(prefix.to_string()),
     )
     .consistent_read(true)
 }
diff --git a/services/identity/src/error.rs b/services/identity/src/error.rs
index c41844788..1dcbb3cdb 100644
--- a/services/identity/src/error.rs
+++ b/services/identity/src/error.rs
@@ -1,157 +1,164 @@
 use aws_sdk_dynamodb::{model::AttributeValue, Error as DynamoDBError};
 use std::collections::hash_map::HashMap;
 use std::fmt::{Display, Formatter, Result as FmtResult};
 use tracing::error;
 
 #[derive(
   Debug, derive_more::Display, derive_more::From, derive_more::Error,
 )]
 pub enum Error {
   #[display(...)]
   AwsSdk(DynamoDBError),
   #[display(...)]
   Attribute(DBItemError),
   #[display(...)]
   Transport(tonic::transport::Error),
   #[display(...)]
   Status(tonic::Status),
   #[display(...)]
   MissingItem,
+  #[display(...)]
+  DeviceList(DeviceListError),
+}
+
+#[derive(Debug, derive_more::Display, derive_more::Error)]
+pub enum DeviceListError {
+  ConcurrentUpdateError,
 }
 
 #[derive(Debug, derive_more::Error, derive_more::Constructor)]
 pub struct DBItemError {
   pub attribute_name: String,
   pub attribute_value: Option<AttributeValue>,
   pub attribute_error: DBItemAttributeError,
 }
 
 impl Display for DBItemError {
   fn fmt(&self, f: &mut Formatter) -> FmtResult {
     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(...)]
   InvalidTimestamp(chrono::ParseError),
   #[display(...)]
   ExpiredTimestamp,
   #[display(...)]
   InvalidValue,
 }
 
 pub trait FromAttributeValue {
   fn to_vec(
     &self,
     attr_name: &str,
   ) -> Result<&Vec<AttributeValue>, DBItemError>;
   fn to_string(&self, attr_name: &str) -> Result<&String, DBItemError>;
   fn to_hashmap(
     &self,
     attr_name: &str,
   ) -> Result<&HashMap<String, AttributeValue>, DBItemError>;
 }
 
 fn handle_attr_failure(value: &AttributeValue, attr_name: &str) -> DBItemError {
   DBItemError {
     attribute_name: attr_name.to_string(),
     attribute_value: Some(value.clone()),
     attribute_error: DBItemAttributeError::IncorrectType,
   }
 }
 
 impl FromAttributeValue for AttributeValue {
   fn to_vec(
     &self,
     attr_name: &str,
   ) -> Result<&Vec<AttributeValue>, DBItemError> {
     self.as_l().map_err(|e| handle_attr_failure(e, attr_name))
   }
 
   fn to_string(&self, attr_name: &str) -> Result<&String, DBItemError> {
     self.as_s().map_err(|e| handle_attr_failure(e, attr_name))
   }
 
   fn to_hashmap(
     &self,
     attr_name: &str,
   ) -> Result<&HashMap<String, AttributeValue>, DBItemError> {
     self.as_m().map_err(|e| handle_attr_failure(e, attr_name))
   }
 }
 
 pub trait AttributeValueFromHashMap {
   fn get_string(&self, key: &str) -> Result<&String, DBItemError>;
   fn get_map(
     &self,
     key: &str,
   ) -> Result<&HashMap<String, AttributeValue>, DBItemError>;
   fn get_vec(&self, key: &str) -> Result<&Vec<AttributeValue>, DBItemError>;
 }
 
 impl AttributeValueFromHashMap for HashMap<String, AttributeValue> {
   fn get_string(&self, key: &str) -> Result<&String, DBItemError> {
     self
       .get(key)
       .ok_or(DBItemError {
         attribute_name: key.to_string(),
         attribute_value: None,
         attribute_error: DBItemAttributeError::Missing,
       })?
       .to_string(key)
   }
 
   fn get_map(
     &self,
     key: &str,
   ) -> Result<&HashMap<String, AttributeValue>, DBItemError> {
     self
       .get(key)
       .ok_or(DBItemError {
         attribute_name: key.to_string(),
         attribute_value: None,
         attribute_error: DBItemAttributeError::Missing,
       })?
       .to_hashmap(key)
   }
 
   fn get_vec(&self, key: &str) -> Result<&Vec<AttributeValue>, DBItemError> {
     self
       .get(key)
       .ok_or(DBItemError {
         attribute_name: key.to_string(),
         attribute_value: None,
         attribute_error: DBItemAttributeError::Missing,
       })?
       .to_vec(key)
   }
 }
 
 pub fn consume_error<T>(result: Result<T, Error>) {
   match result {
     Ok(_) => (),
     Err(e) => {
       error!("{}", e);
     }
   }
 }