Spring Boot with Read Replica

This comprehensive demo will walk you through implementing a master-slave database architecture in Spring Boot, where write operations target the master database while read operations are distributed across read replicas.

The Problem We're Solving

Performance Bottlenecks in Single Database Architecture

Traditional Spring Boot applications typically connect to a single database instance, creating several critical issues:

• Read/Write Contention: All database operations compete for the same resources, causing performance degradation

• Single Point of Failure: Database downtime means complete application unavailability

• Limited Scalability: Cannot independently scale read and write operations

• Resource Competition: Complex read queries can block critical write operations

Real-World Scenario

Consider an e-commerce application handling:

• Product catalog browsing: Heavy read operations (product details, search, filtering)

• Order processing: Critical write operations that cannot be delayed

• Analytics queries: Resource-intensive reporting that shouldn't impact user experience

Without read replicas, a complex analytics query could significantly slow down order processing, directly impacting revenue and user experience.

Our Solution: Master-Slave Architecture with Spring Boot

Architecture Overview

We'll implement a dual-datasource configuration that intelligently routes database operations:

text┌─────────────────┐    ┌──────────────────┐
│   Spring Boot   │    │   Master DB      │
│   Application   │────┤   (Writes)       │
│                 │    │                  │
│                 │    └──────────────────┘
│                 │           │
│                 │           │ Replication
│                 │           ▼
│                 │    ┌──────────────────┐
│                 │────┤   Read Replica   │
└─────────────────┘    │   (Reads)        │
                       └──────────────────┘

Key Components We'll Build

1. Dual DataSource Configuration

• Primary DataSource: Handles all write operations (INSERT, UPDATE, DELETE)

• Read-Only DataSource: Dedicated to read operations (SELECT queries)

• Connection pooling optimization for each datasource type

2. Custom Routing Logic

• @Transactional(readOnly = true) annotation detection

• Dynamic datasource switching based on operation type

• Fallback mechanisms when read replica is unavailable

3. Repository Layer Enhancement

• Service-level transaction management

• Method-level routing for granular control

• Read/write operation separation in business logic

Technical Implementation Approach

Our solution leverages Spring's AbstractRoutingDataSource to create a smart proxy that:

1. Intercepts database calls before they reach the actual datasource

2. Analyzes the transaction context to determine operation type

3. Routes to appropriate datasource based on predefined rules

4. Maintains transaction integrity across different datasources

Expected Benefits

After implementing this architecture, you'll achieve:

• 30-70% improvement in read query performance through dedicated resources

• Reduced master database load enabling faster write operations

• Enhanced fault tolerance with read replica failover capabilities

• Horizontal scalability by adding more read replicas as needed

• Better resource utilization with optimized connection pooling