Senior Backend Java Developer (Microservices)

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

Job summary

Optimum Solutions (Singapore) Pte Ltd. is seeking an experienced Senior Backend Java Developer with a focus on microservices architecture, distributed systems, and backend engineering.

You will design, build, and scale microservices-based RESTful APIs and enterprise backend components, focusing on service communication, asynchronous messaging, and sound microservice design across the stack. The role emphasizes Spring Boot, Java concurrency, database optimization, and robust API/security

Qualifications

• 5+ years of hands-on Java software development experience.
• Strong knowledge of Collections, Streams API, and concurrency.
• Experience with Spring Boot, Spring Core, Spring MVC, and DI.
• Deep microservices and distributed systems understanding.
• Proficient in SQL tuning, data persistence, and Spring Data JPA.
• Experience with testing (JUnit, Mockito) and TDD.

Responsibilities

• Design, build, and maintain scalable microservices using Java and Spring Boot.
• Implement clean microservice patterns, domain-driven design, and reusable modules.
• Document REST endpoints with OpenAPI/Swagger.
• Leverage concurrency and asynchronous messaging for performance.
• Diagnose memory leaks and GC bottlenecks in containerized environments.
• Model relational and NoSQL schemas for decoupled services.
• Manage data persistence and transactions with Spring Data JPA.
• Write optimized SQL queries and implement caching (e.g., Redis).
• Apply resiliency patterns like circuit breakers, rate limiting, retries.
• Implement API security (OAuth2, JWT) and data sanitization.
• Implement structured logging, health checks, and metrics.
• Write unit tests and participate in code/architecture reviews.

Skills

Java

Spring Boot

Microservices

Multithreading

JUnit/Mockito

SQL

Tools

Spring Data JPA

Redis

CI/CD

Swagger/OpenAPI

OAuth2/JWT

Job description

Position Overview

We are seeking an experienced Senior Backend Java Developer with a specialized 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, optimizing database interactions, and driving sound microservice design principles across the stack.

Responsibilities

• 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 containerized environments.
• Design and optimize 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, authorization, and data sanitization).
• 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.

Requirements

• 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.