LowFile-scopePython Plug & play

Optimize client initialization patterns

Instantiate expensive clients (DB/HTTP/SDK) once and inject/reuse them; avoid per-call construction.

Why this matters

Reduces connection churn and improves throughput.

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

Avoid

def handler():
    client = HttpClient()
    return client.get(url)

Prefer

class Service:
    def __init__(self, client: 'HttpClient'):
        self.client = client
    def handler(self):
        return self.client.get(url)

Bad

HttpClient() in every function

Good

Service(HttpClient()).handler()

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