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Sumit Kumar

Deconstructing a Masterclass: Postgres 42,000x Slower

/ 2 min read

postgres, database, performance, tuning, dev-culture

I just came across an absolutely brilliant and hilarious blog post by Jacob Jackson titled “Making Postgres 42,000x slower because I am unemployed”.

It’s such a refreshing take on performance tuning. Instead of the usual struggle for marginal gains, the author embarks on a glorious mission to completely destroy a database’s performance using only its configuration file.

The beauty of the article is how much it teaches you about Postgres internals by showing you exactly how to break them. It’s a masterclass in reverse-engineering performance.

I was interested in this article due to my intereset and further working in Databases

The Major Tweaks to Kill Performance

The author’s approach was both methodical and malicious. Here are the major tweaks they used to systematically cripple the database:

  • Destroying the Cache: The first and most devastating blow was gutting the shared_buffers. By slashing the RAM cache to its absolute minimum, they forced nearly every query to read from the slow disk instead of fast memory.

  • Weaponizing Background Work: They reconfigured the autovacuum process to run constantly and aggressively. This created a state of perpetual, useless “busywork” that consumed system resources for no reason.

  • Making Writes Inefficient: They manipulated the Write-Ahead-Log (WAL) to make every single database write as slow as possible, forcing frequent and expensive flush-to-disk operations (checkpoints).

  • Tricking the Query Planner: In a particularly clever move, they didn’t delete the indexes but made them useless. By setting the random_page_cost to an absurdly high number, they tricked Postgres into thinking a full table scan was always faster than a targeted index lookup.

  • Creating an I/O Bottleneck: The final nail in the coffin was using new configuration options to force all disk Input/Output (I/O) operations through a single, overwhelmed worker thread.

The final result was a staggering 42,000x slowdown, taking a high-performance database and making it completely unusable.

It’s one of the best articles I’ve read on database internals precisely because it comes at the problem from such a unique and destructive angle. You learn more about making Postgres fast by reading how to make it slow. 🔥 I will definitely recommend all the people to just go through this blog. It is awesome.