diff --git a/services/backup/src/Constants.h b/services/backup/src/Constants.h
--- a/services/backup/src/Constants.h
+++ b/services/backup/src/Constants.h
@@ -18,9 +18,9 @@
 // than the chunk limit, once we get the amount of data of size equal to the
 // limit, we wouldn't know if we should put this in the database right away or
 // wait for more data.
-// 400KB limit (KB, not KiB, that's why it's 1000 not 1024) -
+// 400KiB limit (in docs there is KB but they mean KiB) -
 // https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/ServiceQuotas.html
-const size_t LOG_DATA_SIZE_DATABASE_LIMIT = 400 * 1000;
+const size_t LOG_DATA_SIZE_DATABASE_LIMIT = 1024 * 400;
 
 } // namespace network
 } // namespace comm
diff --git a/services/commtest/tests/backup_test.rs b/services/commtest/tests/backup_test.rs
--- a/services/commtest/tests/backup_test.rs
+++ b/services/commtest/tests/backup_test.rs
@@ -13,8 +13,8 @@
 
 use backup_utils::{BackupData, Item};
 use bytesize::ByteSize;
-use tools::get_grpc_chunk_size_limit;
 use tools::Error;
+use tools::{get_dynamo_db_item_size_limit, get_grpc_chunk_size_limit};
 
 use backup_utils::BackupServiceClient;
 
@@ -30,25 +30,30 @@
       String::new(),
       vec![ByteSize::mib(1).as_u64() as usize; 6],
       vec![
+        "holder0".to_string(),
         "holder1".to_string(),
         "holder2".to_string(),
-        "holder3".to_string(),
       ],
     ),
     log_items: vec![
-      Item::new(String::new(), vec![ByteSize::b(100).as_u64() as usize], vec!["holder1".to_string()]),
+      // the item that almost hits the DB limit, we're going to later add a long
+      // list of attachments, so that causes it to exceed the limit.
+      // In this case its data should be moved to the S3
       Item::new(
         String::new(),
-        vec![ByteSize::kb(400).as_u64() as usize],
-        vec!["holder2".to_string(), "holder3".to_string()],
+        vec![get_dynamo_db_item_size_limit() - ByteSize::b(100).as_u64() as usize],
+        vec!["holder0".to_string(), "holder1".to_string()],
       ),
+      // just a small item
+      Item::new(String::new(), vec![ByteSize::b(100).as_u64() as usize], vec!["holder0".to_string()]),
+      // a big item that should be placed in the S3 right away
       Item::new(
         String::new(),
         vec![get_grpc_chunk_size_limit(), get_grpc_chunk_size_limit()],
         vec![
+          "holder0".to_string(),
           "holder1".to_string(),
           "holder2".to_string(),
-          "holder3".to_string(),
         ],
       ),
     ],
@@ -122,5 +127,39 @@
     );
   }
 
+  // push so many attachments that the log item's data will have to be moved
+  // from the db to the s3
+  let mut attachments_size = 0;
+  let mut i = backup_data.log_items[0].attachments_holders.len();
+  let mut new_attachments: Vec<String> = vec![];
+  while attachments_size < 500 {
+    let att = format!("holder{}", i);
+    attachments_size += att.len();
+    new_attachments.push(att);
+    i += 1;
+  }
+
+  let mut old_attachments =
+    backup_data.log_items[0].attachments_holders.clone();
+  backup_data.log_items[0].attachments_holders = new_attachments;
+  add_attachments::run(&mut client, &backup_data, Some(0)).await?;
+  backup_data.log_items[0]
+    .attachments_holders
+    .append(&mut old_attachments);
+  let result = pull_backup::run(&mut client, &backup_data).await?;
+  // check logs attachments
+  for i in 0..backup_data.log_items.len() {
+    let expected: usize = backup_data.log_items[i].attachments_holders.len();
+    let from_result: usize = result.log_items[i].attachments_holders.len();
+    assert!(
+      from_result == expected,
+      "after attachment add: log {}: number of attachments holders do not match,
+      expected {}, got {}",
+      i,
+      expected,
+      from_result
+    );
+  }
+
   Ok(())
 }
diff --git a/services/commtest/tests/lib/tools.rs b/services/commtest/tests/lib/tools.rs
--- a/services/commtest/tests/lib/tools.rs
+++ b/services/commtest/tests/lib/tools.rs
@@ -1,7 +1,10 @@
 use bytesize::ByteSize;
 
 #[allow(dead_code)]
-pub fn generate_nbytes(number_of_bytes: usize, predefined_byte_value: Option<u8>) -> Vec<u8> {
+pub fn generate_nbytes(
+  number_of_bytes: usize,
+  predefined_byte_value: Option<u8>,
+) -> Vec<u8> {
   let byte_value = predefined_byte_value.unwrap_or(b'A');
   return vec![byte_value; number_of_bytes];
 }
@@ -18,6 +21,11 @@
   TonicStatus(tonic::Status),
 }
 
+#[allow(dead_code)]
+pub fn get_dynamo_db_item_size_limit() -> usize {
+  ByteSize::kib(400).as_u64() as usize
+}
+
 pub const GRPC_METADATA_SIZE_BYTES: usize = 5;
 
 #[allow(dead_code)]