fix(cache): add missing token cache invalidation and access token expiry jitter

[appleboy]

Summary

Fix token cache invalidation gaps, add access token expiry jitter, and align all token/cache defaults for a workday-optimized deployment.

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Problem

Two issues identified during code review:

1. Cache invalidation bug: RevokeUserAuthorization() and RevokeAllApplicationTokens() revoked tokens in DB but did NOT invalidate the token cache. With Redis Aside Cache enabled, revoked tokens could pass validation for up to the cache TTL.

2. Thundering herd on token refresh: When many users log in at the same time (e.g., 9:00 AM), all tokens expire simultaneously, causing a spike of refresh requests.

Solution: Redis Aside Cache as Primary Strategy

After comparing two approaches with 20,000 concurrent users, we chose Redis Aside Cache over short-lived stateless tokens:

Metric	Stateless (5min token)	Redis Aside Cache (10h token)
DB operations/sec	~133 (frequent refresh)	~1.4
Token revocation latency	Up to 5 minutes	~milliseconds (RESP3 push)
Frontend complexity	Frequent refresh + retry	Low (10h refresh cycle)

Redis Aside Cache wins by 95x on DB load while achieving near-instant revocation.

How Revocation Works

Admin revokes token
  1. DB: UPDATE status = "revoked"
  2. Redis: DEL cache key
  3. Redis RESP3 pushes invalidation to all Pods
  4. Each Pod's client-side cache evicts the token
  5. Next ValidateToken: cache miss -> DB -> "revoked" -> rejected
  Total latency: ~milliseconds

Cache TTL Design

Two-layer cache with TTLs serving as fallback only (RESP3 handles real-time invalidation):

Layer	TTL	Purpose
Redis server cache	10h (= JWT_EXPIRATION)	Token lives in cache for its entire lifetime; zero DB re-queries
Pod client-side cache	1h	Fallback for missed RESP3 notifications; ~5.6 Redis ops/s for 20K users

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Changes

1. Cache Invalidation Fix (Bug)

• Add GetActiveTokenHashesByAuthorizationID and GetActiveTokenHashesByClientID store methods
• Export InvalidateTokenCacheByHashes on TokenService for cross-service use
• Inject TokenService into AuthorizationService
• Collect token hashes before revocation, invalidate cache after
• Log errors on hash collection failures (consistent with existing patterns)

2. Access Token Expiry Jitter

New JWT_EXPIRATION_JITTER env var adds random offset to access token expiry:

JWT_EXPIRATION=10h
JWT_EXPIRATION_JITTER=30m  # token lifetime: [10h, 10h30m)

• Additive jitter (configured expiry is minimum lifetime)
• Only applies to access tokens, not refresh or client credentials tokens
• Uses math/rand/v2 (Go 1.22+, concurrency-safe)

3. Production-Ready Defaults

All defaults aligned for a typical workday scenario:

Setting	Old Default	New Default	Rationale
JWT_EXPIRATION	1h	10h	One login covers a full workday
JWT_EXPIRATION_JITTER	0 (disabled)	30m	Spread refresh requests over 30min window
TOKEN_CACHE_TTL	5m	10h	Cache = token lifetime; RESP3 handles invalidation
TOKEN_CACHE_CLIENT_TTL	30s	1h	RESP3 handles real-time; TTL is fallback only

Recommended Production Configuration

# Token settings (defaults are production-ready)
JWT_EXPIRATION=10h
JWT_EXPIRATION_JITTER=30m

# Refresh token with rotation
ENABLE_REFRESH_TOKENS=true
REFRESH_TOKEN_EXPIRATION=720h
ENABLE_TOKEN_ROTATION=true

# Token cache (Redis Aside)
TOKEN_CACHE_ENABLED=true
TOKEN_CACHE_TYPE=redis-aside
TOKEN_CACHE_TTL=10h
TOKEN_CACHE_CLIENT_TTL=1h

Files Changed (20 files, +538/-263)

Area	Files	Changes
Store	core/store.go, store/token.go	2 new GetActiveTokenHashesBy* methods
Services	services/token.go, services/authorization.go	Cache invalidation fix + TokenService injection
Bootstrap	bootstrap/services.go	Wire TokenService into AuthorizationService
Config	config/config.go	New defaults for JWT/cache TTLs + jitter field
Token	token/local.go	Jitter in GenerateToken()
Docs	.env.example, CLAUDE.md, docs/CONFIGURATION.md	Document all new settings and defaults
Tests	8 test files	Store tests, jitter tests, config validation, constructor updates

Test Plan

• Store method tests: hash collection by authorization ID and client ID
• Jitter config validation: negative, equal to expiry, greater than expiry
• Jitter functional tests: range verification, variation check, refresh token unaffected
• Updated all NewAuthorizationService call sites (5 test files)
• make test -- all tests pass
• make lint -- 0 issues

Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 36.66667% with 57 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
internal/mocks/mock_store.go	0.00%	36 Missing ⚠️
internal/services/authorization.go	14.28%	13 Missing and 5 partials ⚠️
internal/services/token.go	0.00%	2 Missing ⚠️
internal/bootstrap/services.go	0.00%	1 Missing ⚠️

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