Behind the Scenes: How Database Traffic Control Works

By Patrick Reynolds In March, we released Database Traffic Control™, a feature for mitigating and preventing database overload due to unexpectedly expensive SQL queries. For an overview, read the blog post introducing the feature , and to get started using it, read the reference documentation . This post is a deep dive into how the feature works. Background If you already know how Postgres and Postgres extensions work internally, you can skip this section. A single Postgres server is made up of many running processes. Each client connection to Postgres gets its own dedicated worker process , and all SQL queries from that client connection run, one at a time, in that worker process. When a client sends a SQL query, the worker process parses it, plans it, executes it, and sends any results back to the client. Planning is a key step, in which Postgres takes a parsed query and turns it into a step-by-step execution plan that specifies the indexes to use, the order to load rows from multipl