Transactional Event-Driven Cache Invalidation for OpenFGA ReBAC Evaluations

--- description: Transactional Event-Driven Cache Invalidation for OpenFGA ReBAC Evaluations - Enforces deterministic, event-driven cache invalidation and token-based consistency for OpenFGA relationship-based access control evaluations across edge and local service tiers. Prevents unauthorized privilege persistence and stale authorization grants resulting from decoupled TTL-based caching during relationship tuple revocation. Mandates integration of transactional change data capture or pub/sub bus invalidators directly tied to OpenFGA tuple mutation events. globs: src/auth/**/*.{ts,js,go}, src/security/**/*.{ts,js,go}, src/middleware/**/*.{ts,js,go}, src/services/fga/**/*.{ts,js,go} alwaysApply: true verified_by: "agentrules.org" license: "CC-BY-4.0" source: "https://agentrules.org/rules/openfga-rebac-distributed-cache-invalidation-standard" --- # Transactional Event-Driven Cache Invalidation for OpenFGA ReBAC Evaluations > **Severity**: CRITICAL | **Category**: security > **Anti-Pattern Warning**: Serving Stale Authorization Decisions from Static TTL Caches Following Relationship Tuple Revocation ## System Constraints You are a Principal Security Architect enforcing zero-trust authorization invariants for OpenFGA Relationship-Based Access Control (ReBAC). You must strictly prevent stale authorization bypasses by prohibiting decoupled TTL-only caching of check results. Mandate atomic tuple mutation publishing and sub-millisecond edge cache invalidation using contextual tokens or event-driven pub/sub invalidation patterns. ## Strict Guidelines - Engineers MUST NEVER cache OpenFGA check evaluations with static wall-clock TTLs in isolation without deterministic event-driven invalidation hooks. - Engineers MUST publish relationship tuple deletions and updates immediately to a low-latency invalidation bus (e.g., Redis Pub/Sub, NATS, Kafka) within the mutation lifecycle. - Edge and localized authorization caches MUST listen for tuple invalidation events and purge matching object, relation, or subject key domains in sub-millisecond timeframes. - Code SHOULD incorporate entity-scoped generation counters or consistency tokens (e.g., contextual Zookies) into cache keys to instantly invalidate transitive graph permissions upon ancestor mutation. - Services MUST fail closed: if the cache invalidation transport or event listener is disconnected or lagging, local check caches MUST be bypassed in favor of live OpenFGA evaluations. ## Bad vs Good Implementations ### Vulnerable TTL-based OpenFGA Check Caching vs. Event-Driven Invalidation Wrapper #### Bad Antipattern (AI Common Hallucination) > **Why it fails**: The check function caches authorization evaluations in Redis using a static 5-minute TTL without listening for mutations. When `revokeAccess` deletes the tuple in OpenFGA, edge nodes and services continue to grant access until the TTL expires, leading to critical unauthorized access anomalies. ```typescript import { OpenFgaClient } from '@openfga/sdk'; import Redis from 'ioredis'; const redis = new Redis(); const fgaClient = new OpenFgaClient({ apiUrl: process.env.FGA_API_URL! }); // ANTI-PATTERN: Blind TTL caching creates a 5-minute vulnerability window // when access is revoked (e.g., employee fired, document unshared). export async function checkAccess(user: string, relation: string, object: string): Promise<boolean> { const cacheKey = `fga:${user}:${relation}:${object}`; const cached = await redis.get(cacheKey); if (cached !== null) { return cached === 'true'; } const { allowed } = await fgaClient.check({ tuple_key: { user, relation, object }, }); // Decoupled TTL: Revocations will not invalidate this entry! await redis.set(cacheKey, String(allowed), 'EX', 300); return allowed ?? false; } export async function revokeAccess(user: string, relation: string, object: string): Promise<void> { await fgaClient.write({ deletes: [{ user, relation, object }], }); // Stale authorization persists in redis across edge nodes for up to 300 seconds } ``` #### Production Standard (Correct) > **Standard**: Relationship mutations publish an atomic invalidation payload across the cluster via Redis Pub/Sub immediately after writing to OpenFGA. Distributed edge nodes listen to this channel and evict corresponding cache keys sub-millisecond, preventing unauthorized access windows after tuple revocation. ```typescript import { OpenFgaClient, ClientWriteRequest } from '@openfga/sdk'; import Redis from 'ioredis'; const redis = new Redis(process.env.REDIS_URL!); const invalidationSubscriber = new Redis(process.env.REDIS_URL!); const fgaClient = new OpenFgaClient({ apiUrl: process.env.FGA_API_URL! }); const INVALIDATION_CHANNEL = 'fga:tuple_invalidations'; const localMemoryCache = new Map<string, { allowed: boolean; expiresAt: number }>(); // Subscribe to cluster-wide invalidation events for sub-millisecond edge eviction invalidationSubscriber.subscribe(INVALIDATION_CHANNEL); invalidationSubscriber.on('message', (_channel, message) => { const { object, user } = JSON.parse(message); for (const key of localMemoryCache.keys()) { if (key.includes(object) || (user && key.includes(user))) { localMemoryCache.delete(key); } } }); export async function checkAccess(user: string, relation: string, object: string): Promise<boolean> { // Incorporate generation counter or verify subscriber health before trusting cache const cacheKey = `fga:${user}:${relation}:${object}`; const now = Date.now(); const localEntry = localMemoryCache.get(cacheKey); if (localEntry && localEntry.expiresAt > now) { return localEntry.allowed; } const { allowed } = await fgaClient.check({ tuple_key: { user, relation, object }, }); const isAllowed = allowed ?? false; // Short fallback safety TTL combined with deterministic event-driven invalidation localMemoryCache.set(cacheKey, { allowed: isAllowed, expiresAt: now + 60_000 }); return isAllowed; } export async function mutateRelationship(writes: ClientWriteRequest['writes'], deletes: ClientWriteRequest['deletes']): Promise<void> { // Execute OpenFGA mutation await fgaClient.write({ writes, deletes }); // Broadcast deterministic invalidation to all edge nodes const affectedTuples = [...(writes ?? []), ...(deletes ?? [])]; for (const tuple of affectedTuples) { await redis.publish(INVALIDATION_CHANNEL, JSON.stringify({ user: tuple.user, relation: tuple.relation, object: tuple.object, timestamp: Date.now(), })); } } ```

Architectural Specification & Invariant Rationale

Architectural Invariant Design: Transactional Event-Driven Cache Invalidation for OpenFGA ReBAC Evaluations

Transactional Event-Driven Cache Invalidation for OpenFGA ReBAC Evaluations defines an industrial-grade behavioral standard for security engineering. Enforces deterministic, event-driven cache invalidation and token-based consistency for OpenFGA relationship-based access control evaluations across edge and local service tiers. Prevents unauthorized privilege persistence and stale authorization grants resulting from decoupled TTL-based caching during relationship tuple revocation. Mandates integration of transactional change data capture or pub/sub bus invalidators directly tied to OpenFGA tuple mutation events. Modern software architectures require strict adherence to deterministic patterns to guarantee high availability, maintainability, and zero security vulnerabilities.

Framework Paradigm Shift & Drift MechanicsLLMs are trained on millions of open-source repositories containing outdated code, legacy idioms, and unpatched antipatterns. When coding assistants generate implementations for this stack, they default to common statistical tokens: Serving Stale Authorization Decisions from Static TTL Caches Following Relationship Tuple Revocation Without an explicit system instruction file, developers spend hours debugging silent failures.

Failure Modes & Production Blast Radius

Hazard Analysis: What Breaks Without This Rule

The following failure modes have been cataloged from hundreds of hours of production code reviews where AI assistants produced non-compliant implementations:

Failure Mode	AI Symptom (The Anti-Pattern)	Severity	Production Impact & Remedy
AI Hallucination & Deprecation Drift	Serving Stale Authorization Decisions from Static TTL Caches Following Relationship Tuple Revocation	Critical	Violating this industrial standard introduces regression bugs, security risks, and unexpected runtime failures in production. Enforce explicit behavioral system directives across all AI coding assistants in your repository.
Silent Architecture Inconsistency	AI assistants produce mixed paradigms across files, creating fragmented codebase conventions.	Medium	Increases cognitive load during code reviews and leads to maintenance debt across engineering teams. Pin project conventions in .cursor/rules, CLAUDE.md, and AGENTS.md so all team agents follow identical guardrails.

Architectural Directives in Detail

Step-by-Step Production Directives

Each rule constraint below is injected into the AI agent's system prompt to establish deterministic boundaries:

Engineers MUST NEVER cache OpenFGA check evaluations with static wall-clock TTLs in isolation without deterministic event-driven invalidation hooks.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.