Resiliency Comparison: Single‑AZ vs Multi‑AZ vs Multi‑Region
| Category | Single‑AZ | Multi‑AZ (Single Region) | Multi‑Region |
|---|
| Availability Level | Low – No AZ fault tolerance | High – Survives AZ failure | Very High – Survives region failure |
|---|
| Fault Tolerance | Instance‑level only | AZ‑level redundancy | Region‑level redundancy |
|---|
| Data Replication | Local or single‑node | Synchronous across AZs | Asynchronous or semi‑sync across regions |
|---|
| RPO (Recovery Point Objective) | Minutes to hours (backup-based) | Near‑zero (sync replication) | Seconds to minutes (async replication) |
|---|
| RTO (Recovery Time Objective) | Hours (manual recovery) | Seconds to minutes (auto failover) | Minutes to hours (regional failover) |
|---|
| Latency Between Nodes | Lowest (same AZ) | Low (high‑speed inter‑AZ network) | Highest (cross‑region/geo latency) |
|---|
| Service Continuity During Failure | Outage if AZ fails | No major impact – automatic AZ failover | Continues from secondary region after failover |
|---|
| Compliance & Data Residency | Basic | Regional compliance only | Full geo‑compliance and DR support |
|---|
| Cost | Lowest | Moderate (AZ redundancy) | Highest (duplicate infra across regions) |
|---|
| Use Cases | Dev/Test, low‑critical apps | Business‑critical workloads requiring HA | Mission‑critical systems requiring full DR |
|---|
| Strengths | Simple & cost‑effective | High availability & zero data loss | Maximum resilience & geography‑level protection |
|---|
| Weaknesses | No AZ/Region protection | No region‑level DR | Expensive and more operational complexity |
|---|
About the Author : Anurag Pandey | Database cloud Architect | Oracle | SQL Server | PostgreSQL | AI and Data Platform Enthusiast
Anurag Pandey is a Database Architect with expertise in Oracle, PostgreSQL, SQL Server, Linux, and enterprise database platforms and specializes in database architecture, performance tuning, high availability, disaster recovery, cloud modernization, and operational excellence. With extensive experience in enterprise-scale environments, Anurag is passionate about leveraging AI, automation, and modern data platforms to improve reliability, scalability, and business outcomes. He actively contributes to technical communities through knowledge sharing, architecture guidance, and thought leadership in database and data engineering domains.
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