Motoko Performance Optimizations

What This Is

An extensible guide for speeding up Motoko code safely and predictably. It focuses on mechanical, behavior-preserving improvements: allocation reduction, fixed-width arithmetic, block processing, efficient Text building, and clear loop shapes. Use this skill when you want to improve throughput/latency without changing semantics.

• Benchmarking details and harnesses live in: skills/benchmarks-generation/SKILL.md
• Style and safe refactors that often precede perf work: skills/code-improvements/SKILL.md
• Dot-notation improvements that reduce verbosity/overhead: skills/dot-notation-migration/SKILL.md

Quick Wins (General)

• Minimize allocations in hot paths

  • Avoid materializing entire buffers just to iterate (e.g., prefer indexing Blob directly).
  • Reuse lengths and capacities; cache size() calls to a local variable.

• Prefer fixed-width arithmetic in tight loops

  • Keep shifts/masks on Nat32/Nat64 intermediates; avoid widening to Nat mid-loop.