sequenceDiagram

    title: ListService `getItemsFromDb()` Sequence Flow

    participant l1 as ListService
    participant l2 as ListService
    participant ddbu as DynamoDBUtils
    participant ddb as DynamoDB

    l1->>+l2: getItemsFromDb(taskIds)

    l2->>+ddbu: batchGetAll(params)

    note right of ddbu: DynamoDB batchGet call has max limit of 25 items per request, therefore chunk these
    ddbu->>+ddbu: splitBatchGetIntoChunks(params)
    ddbu-->>-ddbu: chunks

    note right of ddbu: now process each chunk, including retries on failed items...
    loop each chunk

        ddbu->>+ddb: results = ddb:batchGet(chunk)
        ddb-->>-ddbu: results

        ddbu->>+ddbu: mergeBatchGetOutput(overallResults, chunkResults)
        ddbu-->>-ddbu: overallResults

        opt has unprocessed keys?
            note right of ddbu: recursive retry until hit max retry limit
            ddbu->>+ddbu: retriedResults = batchGetAll(params)
            ddbu-->>-ddbu: retriedResults
            ddbu->>+ddbu: mergeBatchGetOutput(overallResults, retriedResults)
            ddbu-->>-ddbu: overallResults
        end
    end

    ddbu-->>-l2: overallResults

    l2-->>-l1: items