BookKeeper offers a few APIs that applications can use to interact with it:

• The ledger API is a lower-level API that enables you to interact with ledgers directly
• The Ledger Advanced API is an advanced extension to Ledger API to provide more flexibilities to applications.
• The DistributedLog API is a higher-level API that provides convenient abstractions.

Trade-offs

The Ledger API provides direct access to ledgers and thus enables you to use BookKeeper however you’d like.

However, in most of use cases, if you want a log stream-like abstraction, it requires you to manage things like tracking list of ledgers, managing rolling ledgers and data retention on your own. In such cases, you are recommended to use DistributedLog API, with semantics resembling continous log streams from the standpoint of applications.