feat: Comprehensive Performance Optimizations for Banking Microservices

[devin-ai-integration]

feat: Comprehensive Performance Optimizations for Banking Microservices

Summary

This PR implements a comprehensive set of performance optimizations across all banking microservices as requested. The changes include database connection pooling, Feign client optimization, caching infrastructure, circuit breaker patterns, database indexing, API Gateway rate limiting, JVM tuning, and enhanced monitoring capabilities.

Key Performance Improvements:

• HikariCP Connection Pooling: Configured across all 4 services with 20 max connections, 5 min idle
• Feign Client Optimization: Added Request.Options (5s connect, 10s read) and ApacheHttpClient for better connection pooling
• Database Indexing: Added JPA indexes on frequently queried fields (authId, emailId, userId, accountId, fromAccount, toAccount, referenceId)
• API Gateway Rate Limiting: Implemented Redis-backed rate limiting (10 req/sec, 20 burst capacity)
• Circuit Breaker Patterns: Added Resilience4j configuration for fault tolerance
• JVM Optimization: Configured G1GC with optimized heap settings in Docker containers
• Enhanced Monitoring: Added Micrometer Prometheus registry for metrics collection

Review & Testing Checklist for Human

🔴 HIGH PRIORITY (5 items)

• Dependency Compatibility: Verify that all new dependencies (Redis, Resilience4j, Micrometer, feign-httpclient) are compatible with Spring Boot 2.7.x and Spring Cloud 2021.0.8
• Service Startup: Test that all 5 services (User, Account, Transaction, Fund-Transfer, API-Gateway) start up successfully with the new configurations
• Database Schema Changes: Verify that JPA index annotations don't cause issues with existing data and that schema updates work correctly
• Redis Infrastructure: Ensure Redis server is available and properly configured for both rate limiting and caching functionality
• Inter-Service Communication: Test that Feign client optimizations don't break communication between services (especially Fund-Transfer ↔ Transaction and Fund-Transfer ↔ Account)

Recommended Test Plan:

1. Start Redis server locally
2. Start all microservices in dependency order (Service-Registry → others)
3. Test basic API flows through the API Gateway
4. Verify rate limiting works by making rapid requests
5. Check that database operations complete successfully with new indexes
6. Monitor service health endpoints for any startup issues

---

Diagram

%%{ init : { "theme" : "default" }}%%
graph TB
    subgraph Legend
        L1["Major Edit"]:::major-edit
        L2["Minor Edit"]:::minor-edit  
        L3["Context/No Edit"]:::context
    end
    
    Gateway["API-Gateway<br/>- application.yml<br/>- pom.xml"]:::major-edit
    UserSvc["User-Service<br/>- application.yml<br/>- pom.xml<br/>- User.java<br/>- Dockerfile"]:::major-edit
    AccountSvc["Account-Service<br/>- application.yml<br/>- pom.xml<br/>- Account.java"]:::major-edit
    TransactionSvc["Transaction-Service<br/>- application.yml<br/>- pom.xml<br/>- Transaction.java<br/>- FeignClientConfig.java"]:::major-edit
    FundTransferSvc["Fund-Transfer<br/>- application.yml<br/>- pom.xml<br/>- FundTransfer.java<br/>- FeignClientConfig.java"]:::major-edit
    
    Redis["Redis Server<br/>(Infrastructure)"]:::context
    Database["MySQL Databases<br/>(Schema Changes)"]:::context
    
    Gateway -->|"Rate Limiting"| Redis
    UserSvc --> Database
    AccountSvc --> Database
    TransactionSvc --> Database
    FundTransferSvc --> Database
    
    FundTransferSvc -->|"Feign Client"| AccountSvc
    FundTransferSvc -->|"Feign Client"| TransactionSvc
    
    Gateway -->|"Routes with Rate Limiting"| UserSvc
    Gateway -->|"Routes with Rate Limiting"| AccountSvc
    Gateway -->|"Routes with Rate Limiting"| TransactionSvc
    Gateway -->|"Routes with Rate Limiting"| FundTransferSvc
    
    classDef major-edit fill:#90EE90
    classDef minor-edit fill:#87CEEB  
    classDef context fill:#F5F5F5

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Notes

• Configuration Changes: All application.yml files now include HikariCP, Redis, and Resilience4j configurations
• New Dependencies: Added spring-boot-starter-data-redis, resilience4j-spring-boot2, micrometer-registry-prometheus, and feign-httpclient
• Database Impact: JPA @Index annotations will trigger schema changes on next startup
• Infrastructure Requirements: Redis server must be running for rate limiting and caching features
• Docker Optimization: Only User-Service Dockerfile was updated with JVM parameters (other services may need similar updates)

Link to Devin run: https://app.devin.ai/sessions/d8f8fedf76c84fe9838f7695f3bf1f7a
Requested by: @samfert-codeium

⚠️ Important: This PR includes significant infrastructure changes. Please ensure Redis is available and test thoroughly in a development environment before merging.

[devin-ai-integration]

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