How would you design a zero-downtime AngularJS enterprise system upgrade strategy?

Zero-downtime upgrades in AngularJS rely on blue-green deployments, feature flags, and incremental module replacement.

Enterprise AngularJS systems cannot afford downtime during upgrades. A zero-downtime strategy involves running two parallel versions of the application (blue-green deployment). Traffic is gradually shifted using feature flags or routing rules. At the code level, the strangler pattern allows replacing modules one by one. Backend APIs are versioned to avoid breaking frontend contracts. This ensures continuous availability even during full framework migration.