Senior Backend Java Developer (API & Software Engineering)

re-zoo-me; Singapore; On-site; SGD 120,000 - 180,000; Full time

Job summary

re-zoo-me is seeking an experienced Backend Java Developer to design, build, and maintain high-throughput, secure RESTful APIs and enterprise backend components. You will focus on scalable code, multi-datasource interactions, asynchronous execution, and strong OO/FP practices across the stack.

Responsibilities include API design, documentation, performance tuning, and implementing security, logging, and testing patterns with Java/Spring.

Qualifications

• 5+ years of hands-on software development experience using Java 11/17+ with deep knowledge of Collections, Streams API, Multithreading/Concurrency, Memory Model, and Exception Handling.

Responsibilities

• Design, build, and maintain RESTful APIs and backend services using Java (11+) and the Spring / Spring Boot framework.
• Implement clean architectural patterns, object-oriented design principles (SOLID), and reusable software modules.
• Author standard OpenAPI/Swagger documentation for REST endpoints and internal contracts.
• Leverage Java concurrency utilities, multithreading frameworks, and asynchronous programming patterns to ensure efficient application performance.
• Diagnose, debug, and resolve memory leaks, thread contention, and garbage collection bottleneck issues using Java profiling tools.
• Design and optimize relational (PostgreSQL, MySQL, Oracle) and NoSQL database schemas.
• Manage data persistence and transactional boundaries using Spring Data JPA / Hibernate.
• Write tuned SQL queries, establish effective database indexing, and configure connection pooling and caching strategies (e.g., Redis).
• Implement standard API security mechanisms (OAuth2, JWT authentication, authorization, and data sanitization).
• Build structured logging, health checks, and application metrics using standard logging frameworks (Logback, SLF4J).
• Write clean, maintainable, modular, and unit-tested code using JUnit and Mockito.
• Participate in code reviews, technical architecture reviews, and maintain test coverage across applications.

Skills

Java 11/17+

Spring Boot

REST APIs

JVM Concurrency

JUnit 5

Mockito

Kafka/RabbitMQ

Docker

CI/CD

Tools

Spring Data JPA / Hibernate

Flyway/Liquibase

Redis

Maven/Gradle

OpenAPI/Swagger

Job description

Position Overview

We are seeking an experienced Backend Java Developer with strong core Java capabilities and a deep focus on API design and backend architecture. In this role, you will design, build, and maintain high-throughput, secure RESTful APIs and enterprise backend components. You will focus on writing scalable code, optimising multi-database interactions, mastering asynchronous execution, and driving sound object-oriented and functional programming practices across the stack.

Key Responsibilities

• Design, build, and maintain RESTful APIs and backend services using Java (11+) and the Spring / Spring Boot framework.
• Implement clean architectural patterns, object-oriented design principles (SOLID), and reusable software modules.
• Author standard OpenAPI/Swagger documentation for REST endpoints and internal contracts.
• Leverage Java concurrency utilities, multithreading frameworks, and asynchronous programming patterns to ensure efficient application performance.
• Diagnose, debug, and resolve memory leaks, thread contention, and garbage collection bottleneck issues using Java profiling tools.
• Design and optimize relational (PostgreSQL, MySQL, Oracle) and NoSQL database schemas.
• Manage data persistence and transactional boundaries using Spring Data JPA / Hibernate.
• Write tuned SQL queries, establish effective database indexing, and configure connection pooling and caching strategies (e.g., Redis).
• Implement standard API security mechanisms (OAuth2, JWT authentication, authorization, and data sanitization).
• Build structured logging, health checks, and application metrics using standard logging frameworks (Logback, SLF4J).
• Write clean, maintainable, modular, and unit-tested code using JUnit and Mockito.
• Participate in code reviews, technical architecture reviews, and maintain test coverage across applications.

Required Technical Qualifications

• 5+ years of hands-on software development experience using Java 11/17+ with deep knowledge of Collections, Streams API, Multithreading/Concurrency, Memory Model, and Exception Handling.
• Strong expertise in Spring Boot, Spring Core, Spring MVC, and dependency injection paradigms.
• Deep understanding of RESTful architectural styles, HTTP status codes, JSON payload processing, custom middleware, and error-handling patterns.
• Advanced proficiency in Spring Data JPA / Hibernate, multi-datasource routing, raw SQL query tuning, and database migration tooling (Flyway/Liquibase).
• Practical experience with message brokers and event streaming architectures using Kafka or RabbitMQ.
• Solid grasp of Design Patterns (Factory, Builder, Singleton, Strategy), TDD/unit testing principles (JUnit 5, Mockito), and build tools (Maven / Gradle).

Preferred Qualifications

• Understanding of containerization basics (Docker) and modern CI/CD deployment workflows.
• Familiarity with microservice resiliency concepts (Rate Limiting, Circuit Breakers, Retry policies).
• Experience with caching layers and distributed system synchronization.