> then asking the machine for a whole bucketful of data, which should be a superset of what you're actually looking for. For something like a user's transaction

> then asking the machine for a whole bucketful of data, which should be a superset of what you're actually looking for. For something like a user's transactions you'll want to have basically everything there at once, so loading the "order history" page for the past month might be a single query that just returns a report: no joins at all, very fast, super scalable. Not really a superset, cassandra (and scylla, and bigtable, all of which are basically copying bigtable's model) each try very hard not to read any extra data at all, and can often return approximately the exact data requested, modulo serialization data which is usually fitting in ~compression chunk size (64k) + checksum. > If you're using Cassandra and you're also not a fool, it's probably because you actually need a lot of scale Cassandra also gives you very literally the most control over CAP tradeoffs of any database in the industry. If you have 100 machines per DC in each of 10 dcs, what happens when one machine is offline? one rack? one dc? 2 dcs separated from 8? 6 dcs separated from 4? There's no single answer in cassandra (depends on replication factor, consistency of writes, consistency of reads, all of which are tunable, with 2 of those being tunable PER QUERY), the CAP tradeoffs are yours and yours alone. That flexibility is powerful for power users (it's also confusing for novices, which is unfortunate). But to your first point, yes, the point is scale. The lack of opinions and deliberate functionality are designed to enable it to scale to thousands of hosts, potentially petabytes of data, trivially accessible in a single SQL-like CQL query, with realistic read latency < 1ms mean/avg and < 5ms p99 for a tuned workload where you know what you're doing. A lot of users will never need a database that can do a million reads per second across a thousand machines reaching p50 1ms on 2 petabytes of data, but Cassandra can do that, and you don't have to build a whole sharding layer on top of mysql/postgres/redis or even install Scylla to get there.