request path

Walk of GET /alice/stats with Redis on. platform="tuf". TUF is the sibling that also speaks Upstash REST besides a wire URL.

1. CORS middleware (added first, runs second).
2. CacheRateLimitMiddleware with platform="tuf" (added last, runs first).
3. Skip check. Path is not /, /docs, /redoc, /openapi.json, /favicon.ico. Method is GET. Redis is on.
4. Handle is the first path segment, lowercased: alice.
5. Cache key is cache:tuf:{sha256(GET:/alice/stats:sorted_query)}.
6. On HIT, body is base64-decoded and returned with X-Cache: HIT. Done.
7. Negative key invalid:tuf:alice. On HIT, HTTP 404 User does not exist, X-Cache: NEGATIVE-HIT. Invalid-user rate limits apply (10/IP and 5/handle per 10 minutes).
8. Live limits: 60 req/min per IP, 30 req/min per handle. Over: 429 with Retry-After and exponential backoff 5s to 300s.
9. Route fetch_dsa_progress. Contests, rating, and badges still call that fetch so a missing user 404s, then return empty models.
10. make_envelope wraps it. HTTP 200 cached for 3600s unless Cache-Control says otherwise. X-Cache: MISS.

Without Redis, steps 5 to 8 disappear. Every GET hits backend-go.takeuforward.org. Rate limits disappear too.

redis_enabled() is true if TUF_REDIS_URL or REDIS_URL is set, or both UPSTASH_REDIS_REST_URL and UPSTASH_REDIS_REST_TOKEN. Integer knobs also accept a TUF_ prefix (TUF_API_CACHE_TTL_SECONDS wins over API_CACHE_TTL_SECONDS).

Invalid-user markers add "username not found" on top of the family list. TUF’s Go backend uses that wording.

sequenceDiagram
  participant B as Browser
  participant MW as CacheRateLimit
  participant R as Redis or Upstash
  participant RT as stats route
  participant GO as backend-go.takeuforward.org

  B->>MW: GET /alice/stats
  MW->>R: GET cache:tuf:digest
  alt hit
    R-->>MW: body
    MW-->>B: 200 X-Cache HIT
  else miss
    MW->>R: GET invalid:tuf:alice
    MW->>R: INCR rl:ip and rl:handle
    MW->>RT: call_next
    RT->>GO: v1/progress/dsa/alice
    RT-->>MW: envelope
    MW->>R: SETEX cache 3600s
    MW-->>B: 200 X-Cache MISS
  end

IP is X-Forwarded-For first hop, else X-Real-IP, else request.client.host.

/playground is not in SKIP_PATHS. With Redis on, the first path segment is treated as handle playground. Playground sample handle is striver.

Wire URL or Upstash REST. Redis errors fail open: cache miss, rate limit allow.

Keys:

• cache:tuf:{sha256}
• invalid:tuf:{handle}
• rl:ip:tuf:{ip} / rl:handle:tuf:{handle}
• backoff:{same} / violations:{same}