Every Millisecond Counts
A technical case study detailing how a software team optimized ClickHouse database queries from over a minute to sub-second latency. The process involved incremental improvements to data handling and engine configurations rather than single complex tricks.
Why it matters
Efficient database management is critical for scaling high-performance applications and reducing operational costs for large-scale data processing.
Imagine you join a new project with a clear goal, improve ClickHouse performance, so our biggest customers can run their queries in a reasonable amount of time. This is something you’ve done lots of times before. You ask for the most expensive query since it’s usually the one that will have the most impact and a few low-hanging fruit improvements. You run it and it takes more than a minute to complete.
1 row in set. Elapsed: 85.715 sec. Processed 1.96 billion rows, 198.69 GB Peak memory usage: 23.05 GiB. The query is one of the twelve being run in parallel, each computing its own metric or sparkline. And they are in the first screen a client lands on when accessing the application. Imagine a client looking at a spinner for at least a couple of minutes right after logging in.
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