LowFile-scopeKotlin Plug & play

Define constants to avoid re-creation

Hoist constant Regex/Formatters/Collections into top-level vals or companion objects; avoid recreating in hot paths.

Why this matters

Cuts allocations and GC pressure.

Side-by-side examples engineers can pattern-match during review.

Avoid

fun ok(s: String) = Regex("^[a-z]+$").matches(s)

Prefer

private val LOWER = Regex("^[a-z]+$")
fun ok(s: String) = LOWER.matches(s)

Bad

SimpleDateFormat(pattern) each call

Good

val fmt = DateTimeFormatter.ISO_INSTANT

From the same buckets as this rule.

Critical
Avoid Blocking Calls to Async Methods
Blocking async methods with `.Result` or `.Wait()` can cause deadlocks and prevent efficient asynchronous execution. Use `await` instead for proper async behavior.
concurrency-safetyperformance-efficiency
Critical
Fingerprint assets and cache immutably
All static JS/CSS/font/image files MUST use content-hashed filenames (e.g., app.9c1a7b.js) and be served with "Cache-Control: public, max-age=31536000, immutable". HTML and other non-fingerprinted documents MUST be served with "Cache-Control: no-cache" (or equivalent) to enable conditional revalidation.
web-static-assetscaching-strategy+2
Critical
No live network or DB in unit tests—use fakes/mocks
Unit tests must stub or fake external HTTP/DB calls; allow real I/O only in integration/e2e tests tagged accordingly.
testing-qualityperformance-efficiency+1