premature optimization
/prɪˈmætʃər ˌɒptɪmaɪˈzeɪʃən/
CommonMaking code faster before you know what's actually slow.
The quote 'premature optimization is the root of all evil' is from Knuth but usually misused. Knuth was specifically talking about micro-optimizations in hot paths, not all optimization.
Real-world examples4 examples
| # | Example | What it means | Source |
|---|---|---|---|
| 01 | he rewrote the whole query to avoid a join on a table with 200 rows. premature optimization. | The optimization target was too small to matter and added complexity for no benefit. | reddit, 2023 |
| 02 | me: I profiled it and the bottleneck is the DB. coworker: but have you optimized your string formatting. me: ...premature optimization bro | Someone is focused on a tiny issue while the real problem is identified and elsewhere. | x, 2024 |
| 03 | added memoization before writing the tests. king of premature optimization right here | Optimizing before even knowing if the code is correct or if performance matters. | x, 2023 |
| 04 | the Knuth quote gets misused so much. he wasn't saying never optimize. he was saying measure first. | Correcting a common misapplication of the 'premature optimization' concept. | x, 2024 |
Use it when
- Someone is optimizing a code path that runs once on startup.
- A PR sacrifices readability for speed gains that haven't been measured.
- Someone added caching before profiling to find the actual bottleneck.
Do not use it when
- The code has been profiled and the hotspot is confirmed.
- You mean someone is designing for scale too early.Use “over-engineering” instead.
Premature optimization vs over-engineering
premature optimization
Premature optimization is about performance work done before measurement.
VS
over-engineering
Over-engineering is about structural complexity added before it's needed.
Origin and context
The phrase comes from Donald Knuth's 1974 paper 'Structured Programming with go to Statements': 'We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil.' The full quote is almost never used.
- First seen
- 1974
- Confidence
- high
Cite this page
Use this stable URL to reference the entry.
https://slang.fyi/premature-optimizationUpdated: 2026-08-28License: CC BY 4.0