@nestarc/feature-flag

DB-backed feature flags for NestJS + Prisma + PostgreSQL -- tenant-aware overrides, percentage rollouts, and zero external dependencies.

Features

• Database-backed -- flags stored in PostgreSQL via Prisma, no external service required
• Tenant / user / environment overrides -- granular control per tenant, user, or deployment environment
• Percentage rollouts -- deterministic hashing (murmurhash3) for consistent per-user bucketing
• Guard decorator -- @FeatureFlag() automatically gates routes and controllers
• Bypass decorator -- @BypassFeatureFlag() exempts health checks and public endpoints
• Programmatic evaluation -- isEnabled(), evaluateAll(), and findByKey() for service-layer logic
• Detailed evaluation -- evaluateBoolean() returns source, reason, fallback, targeting, bucket, and timing metadata
• Type-safe registries -- defineFlags(), generated clients/decorators, defaults, and lifecycle status helpers
• Pluggable cache -- CacheAdapter interface with built-in MemoryCacheAdapter (default) and RedisCacheAdapter v0.2.0
• Redis Pub/Sub -- cross-instance cache invalidation for horizontal scaling v0.2.0
• Admin REST API -- opt-in FeatureFlagAdminModule with mandatory guard injection v0.2.0
• Repository pattern -- FeatureFlagRepository interface for custom persistence backends v0.2.0
• Tenant context provider -- automatic @nestarc/tenancy integration via TenantContextProvider v0.2.0
• Event system -- optional integration with @nestjs/event-emitter for audit and observability
• Testing utilities -- drop-in TestFeatureFlagModule for unit and integration tests

Installation

npm install @nestarc/feature-flag

Peer dependencies

npm install @nestjs/common @nestjs/core @prisma/client @prisma/adapter-pg pg class-transformer class-validator rxjs reflect-metadata
npm install --save-dev prisma

Version 0.5 requires Prisma 7 and Node.js ^20.19.0, ^22.12.0, or >=24.0.0. See Installation for the generated-client setup. No database migration is required when upgrading from 0.4.

Optional

# Required only if you enable emitEvents
npm install @nestjs/event-emitter

# Required only if you use RedisCacheAdapter
npm install ioredis