A great article, and I am a big fan of algolia, Citus and Redshift. However this article ends up making an odd apples to oranges comparison.<p>They state that "However, achieving sub-second aggregation performances on very large datasets is prohibitively expensive with RedShift", this suggests that they want to do sub-second aggregations across raw event data. However, later in the article, the solution they build is to use rollup tables for sub-second responses.<p>You can also do rollup tables in Redshift, and I can assure you (if you enable the fast query acceleration option) you can get sub-second queries from the rolled up lower-cardinality tables. If you want even better response times, you can store the rollups in plain old Postgres and use something like dblink or postgres_fdw to perform the periodic aggregations on Redshift and insert into the local rollup tables (see [1]). In this model the solution ends up being very similar to their solution with Citus.... and I would predict that this is cheaper than Citus Cloud as Redshift really is a great price point for a hosted system.<p>So the question of performing sub-second aggregations across the raw data remains unanswered... however that really is the ideal end game as you can then offer way more flexibility in terms of filtering than any rollup based solution.<p>Right now, research suggests Clickhouse, Redshift or BigQuery are probably the fastest solutions for that. Not sure about Druid, I dont know it. GPU databasees appear to the be the future of this. I would be interested to see benchmarks of Citus under this use case. I should imagine that Citus is also way better if you have something like a mixed OLAP and OLTP workload (e.g. you need the analytics and the row data to match exactly at all times).<p>Aside: It would be great to see Citus benchmarked against the 1.1 billion taxi rides benchmark by Mark Litwintschik. Any chance of that?<p>[1] <a href="https://aws.amazon.com/blogs/big-data/join-amazon-redshift-and-amazon-rds-postgresql-with-dblink/" rel="nofollow">https://aws.amazon.com/blogs/big-data/join-amazon-redshift-a...</a>
[2] <a href="http://tech.marksblogg.com/benchmarks.html" rel="nofollow">http://tech.marksblogg.com/benchmarks.html</a>