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dobin | 1 year ago

So the TL;DR is: Cassandra and ScyllaDB have bad performance when reading. So they put a cache in front.

discuss

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jhgg|1 year ago

No cache. Just read coalescing. There is a big difference. Coalescing just ensures that while a query is executing if an identical query arrives, rather than sending the same query as an already executing query to the database it will wait for the existing query to complete and duplicate the result. If after this the same query arrives again, it will be issued against the database.

This means we don't have to deal with cache invalidation/consistency issues while also being able to handle thundering herds, for example a large server pinging @everyone and having a bunch of people click into the channel or launch their apps in response.