diff --git a/services/identity/src/database/device_list.rs b/services/identity/src/database/device_list.rs
index 92b9593ab..8dcf36629 100644
--- a/services/identity/src/database/device_list.rs
+++ b/services/identity/src/database/device_list.rs
@@ -1,752 +1,804 @@
 // TODO: get rid of this
 #![allow(dead_code)]
 
 use std::collections::HashMap;
 
 use aws_sdk_dynamodb::{
   client::fluent_builders::Query,
   error::TransactionCanceledException,
   model::{
     AttributeValue, DeleteRequest, Put, TransactWriteItem, Update, WriteRequest,
   },
   output::GetItemOutput,
 };
 use chrono::{DateTime, Utc};
 use tracing::{error, warn};
 
 use crate::{
   client_service::FlattenedDeviceKeyUpload,
   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, 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 DeviceRow {
   pub fn from_device_key_upload(
     user_id: impl Into<String>,
     upload: FlattenedDeviceKeyUpload,
     social_proof: Option<String>,
   ) -> Self {
     Self {
       user_id: user_id.into(),
       device_id: upload.device_id_key,
       device_type: DeviceType::from_str_name(upload.device_type.as_str_name())
         .expect("DeviceType conversion failed. Identity client and server protos mismatch"),
       device_key_info: IdentityKeyInfo {
         key_payload: upload.key_payload,
         key_payload_signature: upload.key_payload_signature,
         social_proof,
       },
       content_prekey: PreKey {
         pre_key: upload.content_prekey,
         pre_key_signature: upload.content_prekey_signature,
       },
       notif_prekey: PreKey {
         pre_key: upload.notif_prekey,
         pre_key_signature: upload.notif_prekey_signature,
       }
     }
   }
 }
 
 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)
   }
 
+  /// Gets user's device list history
+  pub async fn get_device_list_history(
+    &self,
+    user_id: impl Into<String>,
+    since: Option<DateTime<Utc>>,
+  ) -> Result<Vec<DeviceListRow>, Error> {
+    let rows = if let Some(since) = since {
+      // When timestamp is provided, it's better to query device lists by timestamp LSI
+      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 AND #timestamp > :since")
+        .expression_attribute_names("#user_id", ATTR_USER_ID)
+        .expression_attribute_names("#timestamp", ATTR_TIMESTAMP)
+        .expression_attribute_values(
+          ":user_id",
+          AttributeValue::S(user_id.into()),
+        )
+        .expression_attribute_values(
+          ":since",
+          AttributeValue::N(since.timestamp_millis().to_string()),
+        )
+        .send()
+        .await
+        .map_err(|e| {
+          error!("Failed to query device list updates by index: {:?}", e);
+          Error::AwsSdk(e.into())
+        })?
+        .items
+    } else {
+      // Query all device lists for user
+      query_rows_with_prefix(self, user_id, DEVICE_LIST_KEY_PREFIX)
+        .send()
+        .await
+        .map_err(|e| {
+          error!("Failed to query device list updates (all): {:?}", e);
+          Error::AwsSdk(e.into())
+        })?
+        .items
+    };
+
+    rows
+      .unwrap_or_default()
+      .into_iter()
+      .map(DeviceListRow::try_from)
+      .collect::<Result<Vec<DeviceListRow>, 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)
   }
 
   /// Adds new device to user's device list. If the device already exists, the
   /// operation fails. Transactionally generates new device list version.
   pub async fn add_device(
     &self,
     user_id: impl Into<String>,
     device_key_upload: FlattenedDeviceKeyUpload,
     social_proof: Option<String>,
   ) -> Result<(), Error> {
     let user_id: String = user_id.into();
     self
       .transact_update_devicelist(&user_id, |ref mut device_ids| {
         let new_device = DeviceRow::from_device_key_upload(
           &user_id,
           device_key_upload,
           social_proof,
         );
 
         if device_ids.iter().any(|id| &new_device.device_id == id) {
           warn!(
             "Device already exists in user's device list \
               (userID={}, deviceID={})",
             &user_id, &new_device.device_id
           );
           return Err(Error::DeviceList(DeviceListError::DeviceAlreadyExists));
         }
         device_ids.push(new_device.device_id.clone());
 
         // Put new device
         let put_device = Put::builder()
           .table_name(devices_table::NAME)
           .set_item(Some(new_device.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_operation =
           TransactWriteItem::builder().put(put_device).build();
 
         Ok(put_device_operation)
       })
       .await
   }
 
   /// 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(())
   }
 
   /// Deletes all user data from devices table
   pub async fn delete_devices_table_rows_for_user(
     &self,
     user_id: impl Into<String>,
   ) -> Result<(), Error> {
     // 1. get all rows
     // 2. batch write delete all
 
     // we project only the primary keys so we can pass these directly to delete requests
     let primary_keys = self
       .client
       .query()
       .table_name(devices_table::NAME)
       .projection_expression("#user_id, #item_id")
       .key_condition_expression("#user_id = :user_id")
       .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()),
       )
       .consistent_read(true)
       .send()
       .await
       .map_err(|e| {
         error!("Failed to list user's items in devices table: {:?}", e);
         Error::AwsSdk(e.into())
       })?
       .items
       .unwrap_or_default();
 
     let delete_requests = primary_keys
       .into_iter()
       .map(|item| {
         let request = DeleteRequest::builder().set_key(Some(item)).build();
         WriteRequest::builder().delete_request(request).build()
       })
       .collect::<Vec<_>>();
 
     // TODO: We can use the batch write helper from comm-services-lib when integrated
     for batch in delete_requests.chunks(25) {
       self
         .client
         .batch_write_item()
         .request_items(devices_table::NAME, batch.to_vec())
         .send()
         .await
         .map_err(|e| {
           error!("Failed to batch delete items from devices table: {:?}", e);
           Error::AwsSdk(e.into())
         })?;
     }
 
     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)
 }