Citus Hits 10M QPS on Half Neki's Data Nodes

Open-source Citus delivers millions of queries per second more efficiently than Neki, the only other published data point at this scaleLast month PlanetScale published a blog post on how they achieved 118 million queries per second on Neki, their sharded Postgres. It included data points at 5, 50 and 512 shards, and showed the scalability between them.While this was breaking news, our team at StackGres was working on a benchmark to show how we removed Citus' single-coordinator ceiling, allowing Citus to scale without limits. We introduced an architecture in StackGres 1.19 that allows to create as many Query Routers (think of Citus Coordinators, but you can scale them out) as you need. Query Routers scaled near-linearly up to two routers, allowing a three worker cluster to go from 550K queries per second with a single coordinator to 1.4M with three Query Routers.The question then became obvious: can we compare Neki and Citus? Can Citus match, or outperform, with the new Query Routers, Neki? One observation further motivated us: Neki’s numbers show that data nodes were delivering 231K tps. A trained eye would soon recognize that figure as a low per node number for a modern ARM64 server with 64 cores. Certainly there’s overhead on a sharded system, and both Neki and Citus suffer from it. But we believed Citus could do better.And so it did. We matched the 1M and 10M data points. At those data points Citus was able to achieve slightly better performance (with possibly lower latency too, but those numbers were not drilled down in Neki’s post) with 60% and 48% of the data nodes, respectively. The number of Query Routers was half of Neki’s at 1M and the same at 10M. Overall, Neki needed 1.5 to 1.8 times the vCPU to reach Citus performance levels.Our benchmark was created as similar as possible to Neki’s, but they haven’t published all the details about their setup. Our benchmark setup, but also all the code needed to reproduce it anywhere, will be published soon as a follow-up blog post, so that anyone could verify our claims. There’s further discussion on this blog post about the methodology, results and caveats. And one question that we leave open: could we have continued scaling Citus to more than 100M tps?The benchmarkMake no mistake. Achieving 118M qps is no small feat. It really shows what the technology is able to do, and the team behind it. Yet we knew that Citus, with the new Query Routers functionality that we introduced in StackGres, also scaled very …