[Infrastructure] Add load testing suite with k6 for API performance validation

[Penielka]

Description

No load testing exists to validate API performance under realistic traffic. Implement a k6 (or Artillery) test suite that simulates concurrent users hitting key endpoints: course listing, credential verification, enrollment, and analytics queries. Set performance budgets and run in CI on PRs.

Definition of Done

• k6 installed as dev dependency or available in CI
• Load test script simulating 100 concurrent users over 5 minutes
• Scenarios: course browsing (80% read), credential verification (15%), enrollment (5%)
• Performance budgets: p95 latency <500ms, error rate <1%, throughput >50 req/s
• Test data seeding script to populate database before tests
• Tests run against staging environment, not production
• Results output as JSON for trend analysis
• CI job runs smoke test (10 users, 1 minute) on every PR
• Full load test (100 users, 5 minutes) runs on merge to main

Acceptance Criteria

1. k6 run load-test.js executes successfully against local backend
2. Smoke test runs in CI on every PR
3. Performance budgets are checked and failures reported
4. Test results include p50, p95, p99 latencies and error rate
5. Seeded data does not persist to production database

Files to Modify

• New file: tests/load/k6-smoke.js — smoke test (10 users, 1 min)
• New file: tests/load/k6-full.js — full load test (100 users, 5 min)
• New file: tests/load/seed-data.js — test data seeder
• New file: tests/load/config.json — k6 configuration
• .github/workflows/ci.yml — add load test job (smoke test)
• backend/package.json — add k6 or artillery dev dependency
• docker-compose.yml — may add k6 service for local testing

[Menjay7]

Hi! I came across this issue and would love to work on it. I have experience with similar tasks and I'm confident I can investigate, implement a clean solution, and thoroughly test it before submitting a PR. If the issue is still open, I would appreciate it if you could assign it to me. Thank you!

[gloskull]

Hello, I have 4 years of experience delivering solutions for projects like this, covering backend, frontend, and smart contract development. After carefully reviewing your requirements, I have a clear understanding of the task and am confident in my ability to deliver a clean, efficient, and thoroughly tested solution on time. I prioritize code quality, maintainability, and industry best practices throughout the development process.
My PR will be submitted in under 10hours.

[clintjeff2]

Hello, I have 6 years of experience working on tasks like this and handling similar challenges across backend, frontend, and smart-contract development. I have carefully read and fully understood the task requirements, and I am confident I can deliver a clean, efficient, and well-tested solution promptly. I always ensure high-quality implementation, maintainability, and adherence to best practices.

Pull request in 5 hours.