Senior Backend Java Developer (Microservices)

Optimum Solutions Pte Ltd; Singapore; On-site; SGD 120,000 - 180,000; Full time

Job summary

Optimum Solutions Pte Ltd in Singapore is seeking an experienced Senior Backend Java Developer to design, build, and scale microservices-based RESTful APIs and enterprise backend components. You will focus on service communication, asynchronous messaging, database interactions, and sound microservice design across the stack.

The role requires 5+ years of hands-on Java development with Spring Boot, Spring Core, and Spring MVC; knowledge of microservices architecture, REST, Spring Data JPA, SQL

Qualifications

• 5+ years of hands-on Java software development with concurrency knowledge.
• Strong Spring Boot, Spring Core, Spring MVC expertise.
• Deep understanding of microservices architecture and RESTful styles.
• Proficiency in Spring Data JPA, SQL tuning, and database migrations.
• Experience with message brokers and event streaming architectures.
• Familiar with TDD/unit testing (JUnit/Mockito), containerization, and CI/CD.

Responsibilities

• Design, build, and maintain scalable microservices and distributed backend services using Java and the Spring / Spring Boot ecosystem.
• Implement clean microservice architectural patterns, domains and reusable modules.
• Author OpenAPI/Swagger docs for REST endpoints and contracts.
• Leverage Java concurrency and asynchronous messaging for performance.
• Diagnose memory leaks, thread contention, and GC bottlenecks in containerized environments.
• Design and optimize relational and NoSQL DB schemas for decoupled services.
• Write optimized SQL queries, and configure caching strategies (Redis).
• Implement resiliency patterns like Circuit Breakers, Retry, and Rate Limiting.
• Build logging, health checks, and metrics; ensure test coverage with JUnit/Mockito.
• Participate in code and architecture reviews and maintain quality.

Skills

Java

Spring Boot

Spring Core

Spring MVC

Microservices

REST APIs

OpenAPI/Swagger

JUnit

Mockito

CI/CD

Containerization

Redis caching

SQL tuning

Domain-driven design

Concurrency

Job description

We are seeking an experienced Senior Backend Java Developer with a specialised focus on microservices architecture, distributed systems, and backend engineering. In this role, you will design, build, and scale microservices-based RESTful APIs and enterprise backend components. You will focus on service communication, asynchronous messaging, optimising database interactions, and driving sound microservice design principles across the stack.

What you'll do

• Design, build, and maintain scalable microservices and distributed backend services using Java and the Spring / Spring Boot ecosystem.
• Implement clean microservice architectural patterns, domain-driven design, and reusable software modules.
• Author standard OpenAPI/Swagger documentation for REST endpoints and inter-service contracts.
• Leverage Java concurrency utilities and asynchronous messaging to ensure efficient application performance.
• Diagnose, debug, and resolve memory leaks, thread contention, and garbage collection bottlenecks in containerised environments.
• Design and optimise relational and NoSQL database schemas tailored for decoupled microservices.
• Manage data persistence and transactional boundaries across distributed services using Spring Data JPA.
• Write tuned SQL queries, establish effective database indexing, and configure caching strategies (e.g., Redis).
• Implement robust microservice resiliency patterns including Circuit Breakers, Rate Limiting, and Retry policies.
• Implement standard API and service security mechanisms (OAuth2, JWT authentication, authorisation, and data sanitisation).
• Build structured logging, health checks, and application metrics using standard logging frameworks.
• Write clean, maintainable, modular, and unit-tested microservice code using JUnit and Mockito.
• Participate in code reviews, technical architecture reviews, and maintain test coverage across application modules.

What you'll need

• 5+ years of hands-on software development experience using Java with deep knowledge of Collections, Streams API, Multithreading/Concurrency, and Exception Handling.
• Strong expertise in Spring Boot, Spring Core, Spring MVC, and dependency injection paradigms.
• Deep understanding of microservices architecture, distributed systems design principles, and RESTful architectural styles.
• Advanced proficiency in Spring Data JPA, raw SQL query tuning, and database migration tooling.
• Practical, hands-on experience with message brokers and event streaming architectures.
• Solid grasp of Design Patterns, TDD/unit testing principles (JUnit, Mockito), containerization basics, and CI/CD deployment pipelines.

Preferred Qualifications

• Experience with service mesh technologies and cloud-native observability tools.
• Familiarity with major cloud platforms and managed container orchestration services.
• Experience with caching layers, distributed synchronization, and event-driven patterns.