# System strength report

Date: 2026-07-22

## Result

The backend is functionally stable and performs well in the tested local environment. It is not yet possible to claim production-scale capacity because the test used a single Node.js process, local MongoDB, a small dataset, and disabled Redis/S3/Atlas dependencies.

## Verification summary

| Area | Result |
| --- | --- |
| TypeScript build | Passed |
| ESLint | Passed |
| Unit/integration suites | 85/85 passed |
| Unit/integration tests | 947/947 passed |
| End-to-end scenarios | 14/14 passed |
| Dependency audit | 0 cached advisory findings; live audit runs in CI |
| Statement coverage | 93.08% |
| Branch coverage | 67.97% |
| Function coverage | 92.93% |
| Line coverage | 93.26% |

The executable service layer is also protected by an aggregate coverage gate: 92.81% statements,
93.02% lines, 93.67% functions, and 74.96% branches across 43 service files. `npm run
test:coverage` enforces both the project-wide gates and these service-layer gates, and the same
command is mandatory in CI.

## Performance results

Tests ran on one local process and are useful for regression comparison, not public capacity promises.

| Workload | Concurrency | Throughput | Average | p95 | p99 | Success |
| --- | ---: | ---: | ---: | ---: | ---: | ---: |
| Liveness health | 20 | 2357 req/s | 8.47 ms | 12.64 ms | 15.92 ms | 100% |
| Cached personalized feed | 20 | 567 req/s | 35.20 ms | 40.78 ms | 45.25 ms | 100% |
| Liveness burst | 100 | 2448 req/s | 40.71 ms | 48.89 ms | 72.62 ms | 100% |
| Uncached personalized feed | 20 | 65 req/s | 304.34 ms | 392.81 ms | 445.92 ms | 100% |
| Uncached compatibility search | 10 | 109 req/s | 91.38 ms | 100.38 ms | 106.79 ms | 100% |
| Hardened health gate | 50 | 2041 req/s | 24.40 ms | 39.85 ms | 48.57 ms | 100% |
| Cold-cache/coalesced feed gate | 30 | 336 req/s | 88.79 ms | 116.14 ms | 168.69 ms | 100% |

Cold startup was approximately 4.8 seconds.

## Security checks

- Forged JWT was rejected with 401.
- NoSQL-shaped login input was rejected with 400.
- Unknown privileged fields were rejected with 400.
- Malformed JSON was rejected with 400.
- A request above the configured body limit was rejected with 413.
- Login throttling returned 429 after the allowed attempts were consumed.
- Production CORS returned the configured origin and did not return an allow-origin header for an untrusted origin.
- HSTS, X-Frame-Options, X-Content-Type-Options, and Referrer-Policy were present in production mode.
- The npm audit reported zero known vulnerabilities.

## Concurrency and realtime checks

- Twenty simultaneous duplicate like requests produced one like and a correct counter.
- Authenticated Socket.IO clients connected to both `chat` and `notifications` namespaces.
- An anonymous Socket.IO client was disconnected.
- Refresh-token rotation, notification delivery, feed exclusion, comments, uploads, and superadmin sessions passed end-to-end.

## Improvements made during testing

- Added `/api/v1/health/ready`, which checks MongoDB, Redis when enabled, and storage, and returns 503 when degraded.
- Added readiness unit and end-to-end coverage.
- Added real Socket.IO end-to-end tests.
- Added concurrent idempotency coverage for likes.
- Improved startup benchmark diagnostics to include the child exit code and recent logs.
- Corrected local storage configuration to use direct media access.
- Added local single-flight and ownership-safe Redis leases to prevent cache stampedes.
- Added configurable MongoDB connection pools and disabled automatic production index builds by default.
- Added response compression and bounded Node HTTP transport settings.
- Added request deadlines, graceful request draining, and drain-aware readiness.
- Added event-loop, in-flight request, timeout, and bounded-cardinality route metrics.
- Added direct, user-scoped S3 PUT uploads so large media can bypass Node memory.
- Added CI performance gates and made unit, E2E, audit, and Docker build checks mandatory before deployment.
- Added behavioral, security, failure-path, controller-delegation, repository-persistence, and
  bootstrap tests, increasing the regression suite to 947 tests.
- Added enforced project-wide and service-layer coverage gates so the achieved baseline cannot
  silently regress.
- Hardened the production container with a non-root user, `tini`, a healthcheck, and secret-safe Docker context exclusions.

## Remaining production validation

Before a high-traffic launch, run the same tests in staging with production-sized data and production topology:

1. Multiple application replicas behind the real load balancer.
2. Redis enabled for cache, throttling, queues, and Socket.IO fan-out.
3. S3-compatible storage, signed media URLs, and CDN behavior.
4. Atlas Search indexes and representative Arabic/English datasets.
5. Long soak tests (2-8 hours), failover tests, and MongoDB/Redis latency injection.
6. Continue raising branch coverage, prioritizing rare infrastructure and dependency-failure combinations.
7. Run an external DAST/SAST and penetration test before handling sensitive production data.

## Current assessment

- Functional correctness: strong.
- Local performance: strong with cache; acceptable but database-bound without cache.
- Security controls: strong baseline.
- Operational readiness: good after adding dependency readiness checks.
- Automated test maturity: strong baseline, with more than 90% statement, line, and function coverage
  plus separate runtime-service gates.
- Production-scale confidence: pending staging tests with real infrastructure and data volume.