[zorkian]

(I work at Discord in infrastructure.)

We use data services to do "data related things" that make sense to do at a central proxy layer. This may include caching/coalescing/other logic but it doesn't always, it really depends on the particular use case of that data.

For messages, we don't really cache. Coalescing gives us what we want and the hot channel buckets will end up in memory on the database, which is NVMe backed for reads anyway so the performance of a cache wouldn't add much here for this use case.

In other places, where a single user query turns into many database queries and we have to aggregate data, caching is more helpful.