casey-perfchecklisted

# Performance Ballpark Check Quick sanity check: is this code in the right ballpark, or is it leaving 10-100x on the table? ## Conservative Node.js Baselines (V8 JIT warm, any modern machine) These are intentionally low. If code is slower than these, it's definitely a problem. | Operation | ~ops/sec | Order of magnitude | |---|---|---| | Simple arithmetic | 750M | 10^8-9 | | Property access | 200M | 10^8 | | Function call | 200M | 10^8 | | Object allocation | 200M | 10^8 | | Array .map() per element | 100M | 10^8 | | String concat | 50M | 10^7 | Benchmarked on M2 Mac, Node v25. x86 machines may be 30-50% slower. **Python (CPython):** divide Node numbers by ~10-20x. ## The Method 1. **Estimate operations**: How many items? How many ops per item? (loops, function calls, allocations) 2. **Calculate theoretical time**: `items × ops_per_item / baseline_ops_sec` 3. **Compare to actual time**: If actual is 10x+ worse than theoretical, dig in. 4. **Write a baseline**: Simplest possible implementation in the SAME language. 1-3 lines. Measure it. The gap between baseline and their code is the waste. ## Key Principle **Don't compare to hardware limits — compare to the runtime's limits.** The interpreter tax is a given. What you're hunting is the bad-code tax on top of it. ## Common Waste Patterns (where the 10-100x usually hides) - **Allocations in hot loops**: `.map().filter().reduce()` chains creating 3 intermediate arrays - **O(n²) hiding as O(n)**: nested `.find()` or `.