Beginner LevelCloud Computing (AWS/GCP/Azure)
What is the difference between AWS RDS Multi-AZ deployments and Read Replicas?
❓ Interview Prompt: Compare AWS RDS Multi-AZ High Availability (synchronous) vs Read Replicas (asynchronous read scaling).
Amazon Relational Database Service (RDS) provides two distinct mechanisms for database scaling and resilience:
1. RDS Multi-AZ (High Availability & Disaster Recovery):
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Mechanism: Synchronously replicates database writes to a Standby instance in a different Availability Zone.
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Purpose: Automatic failover. If the Primary DB crashes, RDS automatically switches DNS to the Standby in ~60 seconds with zero data loss.
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Note: The Standby instance cannot serve read queries; it is strictly a passive failover target.
2. RDS Read Replicas (Read Performance Scaling):
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Mechanism: Asynchronously replicates data to up to 15 Read Replica instances.
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Purpose: Offloads heavy read traffic ('SELECT' queries) from the primary database.
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Note: Read Replicas can serve active application queries and can span across multiple AWS regions.
Code Implementation Example
typescript
// Express DB Connection Pooling separating Write Primary from Read Replicas
import { Pool } from 'pg';
const primaryDb = new Pool({ host: 'db-primary.company.com' }); // Multi-AZ Primary (Writes)
const readReplicaDb = new Pool({ host: 'db-read.company.com' }); // Read Replica (Reads)
async function getProductCatalog() {
// Direct SELECT queries to Read Replica to offload Primary DB!
const res = await readReplicaDb.query('SELECT * FROM products');
return res.rows;
}💡Directing read queries to RDS Read Replicas to offload Primary DB.
🎯 Interview Key Takeaway
Multi-AZ provides synchronous failover for high availability; Read Replicas provide asynchronous read scaling.
#RDS#Multi-AZ#Read Replicas#Databases#Beginner
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