Hacker News Reader

Comment by MrBuddyCasino | Hacker News Reader

> frequently find myself wanting a light append-only data store for pet projects

As someone who is mystified by that statement: why?

Could be used as an event store. Rather than storing a list of mutable objects as in a normal database, you store the changes themselves as a list of facts. This makes things like replication a lot easier and can be optimized to be much faster than a traditional database.

There's Apache BookKeeper to fill some of those needs.

I've never seen BookKeeper in production. Where would you recommend its use over something like Kafka?

Great, but that's not a product. If you're on board with the CQRS/ES thing, actually building your own should not be difficult. (Ok, so I'm assuming non-distributed DB here, but with a bit of imagination one could also do infinitely(!) scalable CQRS/ES within Bounded Contexts, given the fresh crop of easily understandable/implementable concensus algorithms.)

I've used it as the backing for a time-series database and to store deltas for a state-machine - in both situations I wanted something that understood "POJOs" and didn't require a lot of setup.

Even in the case of multiple non-unique entries, if the stored objects are not meant to be mutable, the API exposes .reverse() to find the most recent.

If you know your data has no duplicate (eg, you want to sort and store a list of cities), you know you don't need to check the already-written objects; you only need to append objects.

Auditing becomes easy. The history of all changes is automatically available.

Reply on news.ycombinator.com