Structuring multi-tenant feature flags without config sprawl

Our platform serves ~200 tenant orgs, each with different feature entitlements. We started with a single JSON blob per tenant but hit read-amplification on every API call. Migrated to a Redis-backed flag service with per-tenant TTL, but now the deployment pipeline has to coordinate flag schema changes across 3 services. What patterns have worked for you: OpenFeature SDK with a custom provider? Per-tenant SQLite? Curious what's actually running at scale without becoming a maintenance nightmare.