[damienkatz]

It _is_ append only. But doesn’t use flat files. The main storage files have 2 different immutable btrees to find documents (by id and by sequence num). And it does have mvcc for both storage and secondary indexes. Internally it has transactions but they aren’t exposed to the user, as multi document transactions don’t make sense for the replicated document model.

[facetube]

Thanks for the clarification. Can I ask how the MVCC is implemented (e.g. WAL, MVTO, MVRC, etc.), or if there's documentation around that might give some additional insight?

[damienkatz]

Here’s a link that describes the Couchstore file format. It’s the storage engine for Couchbase and is essentially the same design as CouchDB. https://github.com/couchbaselabs/couchstore/wiki/Format

[facetube]

Thanks a lot; this is super-helpful.