📋 Description

Implements #104 – Develop Advanced Performance Optimization and Caching: intelligent caching, query optimization, performance monitoring, and regression testing in both the Soroban contract and the NestJS indexer.

Contract: Performance cache module stores a bridge summary (health score + top chains by volume) with 1-hour TTL; admin can invalidate cache; bounded chain iteration for gas; new events for cache compute/invalidate.

Indexer: In-memory cache (60s TTL) for dashboard analytics; dashboard aggregates use SQL SUM/COUNT/AVG instead of full-table loads; GET /health and GET /metrics for load balancers and monitoring; MetricsService tracks cache hit rate and latency; dashboard tests include cache behavior and a 2s latency regression test.

🔗 Related Issue(s)

• Closes Develop Advanced Performance Optimization and Caching #104

🎯 Type of Change

• ✨ New feature (non-breaking change that adds functionality)
• ⚡ Performance improvements

📝 Changes Made

• Contract
  • Added performance.rs: PerformanceManager with get_cached_summary, compute_and_cache_summary, get_or_compute_summary, invalidate_cache(admin); CachedBridgeSummary type; storage keys PERF_CACHE, PERF_TS; events PerfMetricsComputedEvent, PerfCacheInvalidatedEvent.
  • Added get_top_chains_by_volume_bounded in analytics.rs (max 50 chains) for gas-bound cache; kept existing get_top_chains_by_volume for backward compatibility.
  • Wired performance module in lib.rs; public API: get_cached_bridge_summary, compute_and_cache_bridge_summary, invalidate_performance_cache.
  • Added contracts/teachlink/tests/test_performance.rs (registration + type tests).
• Indexer
  • CacheModule (60s TTL, global) in AppModule; DashboardService caches getCurrentAnalytics() with key dashboard:analytics; invalidateDashboardCache() for manual invalidation.
  • Dashboard query optimization: escrow/reward totals via SUM/COUNT/AVG in SQL (no full-table find() + reduce).
  • New PerformanceModule: MetricsService (request count, cache hits/misses, last dashboard ms, uptime), PerformanceController with GET /health and GET /metrics.
  • Dashboard spec: CACHE_MANAGER and MetricsService mocks; cache-hit test; performance regression test (getCurrentAnalytics < 2s); fixed generatedBy/save types in dashboard.service.ts.
  • IMPLEMENTATION.md: new “Performance optimization and caching” section.

🧪 Testing

✅ Pre-Merge Checklist (Required)

• 🧪 Unit Tests: Contract tests include test_performance.rs; indexer: npx jest --testPathPattern="dashboard" passes (7 tests).
• 🔨 Debug Build: cargo build (may require MSVC on Windows; CI runs on Linux).
• 🎯 WASM Build: cargo build -p teachlink-contract --target wasm32-unknown-unknown or .\scripts\check-wasm.ps1 on Windows.
• 📝 Code Formatting: cargo fmt --all -- --check
• 🔍 Clippy Lints: cargo clippy

📋 Test Results

# Indexer dashboard tests
npx jest --testPathPattern="dashboard" --passWithNoTests
 PASS  src/reporting/dashboard.service.spec.ts
  DashboardService
    √ should be defined
    getCurrentAnalytics
      √ should return dashboard analytics with zeroed metrics when no data
      √ should include success rate and health score fields
      √ should return cached result when cache hit
      √ performance: getCurrentAnalytics completes within 2s (regression)
    saveSnapshot
      √ should create and save a dashboard snapshot
    getSnapshots
      √ should return snapshots for period
 Test Suites: 1 passed, 1 total
 Tests: 7 passed, 7 total

🔍 Review Checklist

📝 Code Quality

• My code follows the project's style guidelines
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings or errors

🧪 Testing Requirements

• I have added/updated tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

📚 Documentation

• I have updated the documentation accordingly (IMPLEMENTATION.md)

🔒 Security

• I have not committed any secrets, keys, or sensitive data
• My changes do not introduce known vulnerabilities

🏗️ Contract-Specific (if applicable)

• Storage changes are backward compatible (new keys only)
• Event emissions are appropriate and documented
• Gas/resource usage has been considered (bounded iteration, cache reduces repeated reads)

💥 Breaking Changes

• This PR introduces breaking changes
• N/A: New APIs only; existing behavior unchanged.

📊 Performance Impact

• CPU/Memory: Indexer: lower DB load for repeated dashboard requests (cache); fewer rows loaded (aggregates only). Contract: cached summary reduces repeated heavy reads when callers use get_cached_bridge_summary.
• Gas costs: Contract: bounded get_top_chains_by_volume_bounded caps iteration; cache avoids recompute within TTL.
• Network: No change.

🔒 Security Considerations

• Risks: None identified; cache is in-memory (indexer) and instance storage (contract); invalidation is admin-only on contract.
• Mitigations: N/A.

🚀 Deployment Notes

• Requires contract redeployment (new contract code with performance module)
• Requires data migration: No
• Requires configuration changes: No (indexer cache is default 60s TTL)
• No deployment changes needed for indexer beyond deploy of new code

📋 Reviewer Checklist

• 📝 Code review completed
• 🧪 Tests verified
• 📚 Documentation reviewed
• 🔒 Security considerations reviewed
• 🏗️ Architecture/design reviewed
• ✅ Approved for merge

🎯 Ready for Review:

• Yes, all required checks pass and I'm ready for review
• No, I need to fix some issues first