Senior Backend Java Engineer – API & Architecture

optimum solutions (singapore) pte ltd; Singapore; On-site; SGD 108,000 - 180,000; Full time

Job summary

Optimum Solutions Singapore Pte Ltd is seeking an experienced Backend Java Developer with strong core Java and API design expertise to design, build, and maintain RESTful services.

You will work with Spring Boot, tackle multi-database persistence, asynchronous processing, and ensure robust, scalable backend architecture. The role emphasizes clean code, testing (JUnit), code reviews, and solid OO and functional programming practices across the stack.

Qualifications

• 5+ years of hands-on Java 11/17+ development with strong core API skills.
• Deep knowledge of Spring Boot, Spring Core, Spring MVC and DI.
• Solid RESTful design, HTTP status codes, JSON processing and error handling.
• Advanced PostgreSQL/MySQL/Oracle with Hibernate and Spring Data JPA.
• Experience with Kafka or RabbitMQ for messaging/event streaming.
• Proficiency with design patterns, TDD/unit testing (JUnit 5, Mockito) and build tools (Maven/Gradle).

Responsibilities

• Design, build, and maintain RESTful APIs and backend services using Java 11+ and Spring Boot.
• Implement SOLID, object‑oriented design and reusable modules.
• Author OpenAPI/Swagger documentation for endpoints and contracts.
• Leverage concurrency utilities and asynchronous patterns for performance.
• Diagnose memory leaks and GC bottlenecks using profiling tools.
• Design and optimize relational and NoSQL database schemas.

Skills

Java 11/17+

Spring Boot

RESTful APIs

Concurrency

Streams API

SOLID Design

Tools

PostgreSQL

MySQL

Oracle

Hibernate

Redis

Swagger/OpenAPI

Maven

Gradle

Flyway/Liquibase

Job description

Optimum Solutions Singapore Pte Ltd is seeking an experienced Backend Java Developer with strong core Java and API design expertise to design, build, and maintain RESTful services.

You will work with Spring Boot, tackle multi-database persistence, asynchronous processing, and ensure robust, scalable backend architecture. The role emphasizes clean code, testing (JUnit), code reviews, and solid OO and functional programming practices across the stack.