Comment by memset

It does not implement immediate notification of new submissions because the SQS protocol doesn't have a "push" mechanism, only pull.

The software, however, could support this for a different queue protocol. This is because SQLite is just used as a disk store for queue items. The golang code itself still processes each message before writing to disk. Since that code is "aware" of incoming messages, it could implement an immediate notification mechanism if there was a protocol that supported it.