Walk-in || Java Back End Developer

We are looking for a Java Developer to design, develop, and maintain scalable backend

services using Java and Spring Boot. The primary focus will be on Spring WebFlux and

reactive programming, with some development using Spring MVC and JPA.

Key Responsibilities

• Develop and maintain REST APIs using Spring WebFlux and Project Reactor.
• Build non-blocking and reactive backend services using Mono, Flux, and flatMap.
• Work with R2DBC and PostgreSQL for database operations.
• Manage database schema changes using Flyway.
• Implement transactions for multi-step database operations.
• Integrate with external HTTP APIs while maintaining proper transaction boundaries.
• Develop background jobs using Spring @Scheduled.
• Implement polling mechanisms to track external API status and process final results.
• Develop and maintain webhook integrations, including signature validation.
• Ensure polling and webhook updates do not overwrite each other's state incorrectly.
• Implement in-memory caching using Spring Cache and Caffeine.
• Write unit and integration tests using JUnit, Mockito, Reactor Test,

Testcontainers, and PostgreSQL.

• Implement request validation, OAuth2 authentication, and proper error handling.

Required Skills

• 2+ years of professional experience with Java and Spring Boot.
• Strong experience with Spring WebFlux and reactive programming.
• Good understanding of Mono, Flux, flatMap, and non-blocking programming.
• Strong knowledge of PostgreSQL and SQL.
• Experience designing and developing REST APIs.
• Experience with scheduled jobs, polling, webhooks, and caching.
• Understanding of database transactions and concurrency.

Good to Have

• AWS services such as S3 and CloudWatch.
• Blockchain/Web3 integration using Web3j or similar technologies.
• Spring MVC and JPA.
• OpenFeign and Spring Security.
• Gradle and Docker.
• Experience working with fintech, crypto, or financial backend systems.

Testing & Development

• JUnit and Mockito for unit testing.
• Reactor Test for reactive flows.
• Testcontainers for integration testing.
• PostgreSQL integration testing.
• Experience maintaining clean, readable, and production-ready code.