Feature Flags and Progressive Delivery

Feature flags decouple deployment from release—you ship code dark, then expose it to 5% of tenants while watching error budgets.

Flag taxonomy

Release flags must have ticket-linked removal dates. Ops kill switches stay forever.

Progressive rollout checklist

• Metrics dashboard filtered by flag variant
• On-call knows kill-switch owner
• Database migrations compatible with both paths
• Client apps handle unknown flag states gracefully

NestJS integration

if (await this.flags.isEnabled('new-media-pipeline', { userId })) {
  return this.mediaV2.process(file);
}
return this.mediaV1.process(file);

Evaluate flags server-side for security-sensitive features.

Avoid flag debt

Quarterly audits: delete stale flags and combinatorial test paths they created. Fifty permanent flags means fifty untested permutations.

Progressive delivery reduces blast radius—treat flags as temporary scaffolding, not permanent conditionals.