[gleenn]

If you're implementing immutable DB semantics maybe you should consider Datomic or alternatives because then you get that for free, for everything, and you also get time travel which is an amazing feature on top. It lets you be able to see the full, coherent state of the DB at any moment!

[arter45]

My understanding is that Datomic uses something like Postgres as a storage backend. Am I right?

Also, it doesn't support non-immutable use cases AFAIK, so if you need both you have to use two database technologies (interfaces?), which can add complexity.

[ndr]

Datomic can use various storage services. Yes, pg is one option, but you can have DynamoDB, Cassandra, SQLServer and probably more.

> Also, it doesn't support non-immutable use cases AFAIK

What do you mean? It's append only but you can have CRUD operations on it. You get a view and of the db at any point in time if you so wish, but can support any CRUD use case. What is your concern there?

It will work well if you're read-heavy and the write throughput is not insanely high.

I wouldn't say it's internally more complex than your pg with whatever code you need to make it work for these scenarios like soft-delete.

From the DX perspective is incredibly simple to work on (see Simple Made Easy from Rich Hickey).

[ndr]

Also good real-world use case talk: https://www.youtube.com/watch?v=A3yR4OlEBCA

[arter45]

Thanks, I'll look into it. My current setup for this kind of use cases is pretty simple. You essentially keep an additional field (or key if you're non relational) describing state. Every time you change state, you add a new row/document with a new timestamp and new values of state. Because I'm not introducing a new technology for this use case, I can easily mix mutable and non-mutable use cases in the same databases (arguably even in the same table/collection, although it probably makes little sense at least to me).