AZ-aware reads and remote fallback

AZ-aware reads and remote fallback An architecture diagram generated by Archify. Application · AZ-a · known AZ value · AZ-a Application AZ-a · known AZ value Kafka replica · Matching client.rack · AZ-a Kafka replica Matching client.rack Valkey reader · GLIDE AZ preference · AZ-a Valkey reader GLIDE AZ preference Aurora reader · Managed local members · AZ-a Aurora reader Managed local members Other-AZ targets · Writes · read fallback · Other AZs Other-AZ targets Writes · read fallback Prefer local replica Read Select local reader Write or no local reader AZ-a Other AZs Legend Frontend Database Message bus

Cost and consistency

  • • Local reads reduce some transfer; total cost is not zero
  • • Replication, metadata, and fallback can cross AZs
  • • Check replica lag and read-after-write requirements

Discover the AZ

  • • Ordinary Pod creation precedes node selection
  • • Use binding-time injection or trusted post-scheduling lookup
  • • Match each client’s rack/AZ value to its servers

Test fallback

  • • Kafka falls back to leader without a local replica
  • • GLIDE: local replica, local primary, then remote
  • • Missing local Aurora readers need an app reconnect policy