Use when profiling, diagnosing lag, or setting performance budgets. For code-level micro-optimizations (pooling, throttling, relevance filtering, lazy loading) load roblox-luau-patterns; this skill measures and tunes the engine.

Quick Reference

Profiling Tools

MicroProfiler (Ctrl+F6): Per-frame breakdown: scripts, physics, rendering. Primary tool for finding what's slow.
Developer Console (F9): Stats tab: memory, network, render stats. Server Stats for server-side metrics.
Script Profiler (Ctrl+Alt+F5): Per-script CPU usage and heap allocations.

Performance Targets

Metric	Starting target	Investigate at
Server heartbeat	< 16ms	> 33ms
Client FPS (desktop)	60	< 30
Client FPS (mobile)	45	< 30
Memory	device-specific	sustained growth

"Expensive" means the profiler shows it on a hot frame path (raycasts, clones, large finds, replication-heavy writes). Throttle by judgment from measurements, not a universal number, and re-measure after shipping: profile before and after on representative devices and confirm the targeted metric moved without regressions. Micro-optimizations live in roblox-luau-patterns.

Parallel Luau

Use Actors only after profiling identifies isolatable CPU work.
Workers compute; synchronize before restricted DataModel writes.
SharedTable and mutexes add coordination cost; they do not replace ownership boundaries.

Object Pooling

-- Pre-clone, reuse. get() returns a lease token; release() requires it,
-- so duplicate or foreign releases never re-list the object.
local obj, lease = pool:get()
-- ... use obj ...
pool:release(obj, lease)

Canonical pool code (token-lease ownership): roblox-luau-patterns.

StreamingEnabled Essentials

On by default. Container-scoped: only Workspace descendants stream. ModelStreamingBehavior = Improved streams non-BasePart descendants with their parent Model; Legacy streams only BaseParts.
Streamed-out = parented to nil, not destroyed. Luau refs persist if it streams back.
Config (Studio): target defaults 1024, min 64; set StreamingIntegrityMode; tune from data.
Gotcha: FindFirstChild("DistantPart") returns nil if streamed out. Use WaitForChild with timeout.

Mobile

Profile geometry, textures, particles, UI, and shadows on low-end devices.

Full reference with code examples and API tables: [references/full.md](references/full.md)

npx skills add tabooharmony/roblox-brain --skill roblox-performance