Backend Engineer (Spring Boot, 5+ yrs)

About the role

OhMyHotel is a Supplier Architecture Company that connects hotel inventory across Japan, Korea, and Southeast Asia via direct contracts, CMS, and wholesalers. We are heading toward Top-3 OTA status in Japan and aggressive B2C expansion. Our CTO Office team adopts Claude Code and other AI agents as everyday development partners. You will pair with AI agents to build the core backend behind OhMyHotel's inventory, pricing, reservations, and settlement systems - and help drive AI Transformation (AX) across the whole company, not just engineering.

Responsibilities

• Design and implement new APIs and domain services in OhMyHotel's core backend (inventory, pricing, reservations, payments, settlement).
• Build integrations with external systems (OTAs, CMS, channel managers, PMS, payment gateways) - and guarantee concurrency and correctness.
• Incrementally migrate the accumulated legacy backend to the standard stack (Spring Boot 4.x + CQRS + TDD).
• Use AI agents to automate repetitive work and test-coverage tasks, and contribute to improving in-house AI workflows (prompt and agent design).

Requirements

• 5+ years of web application development and operations experience.
• Hands-on RESTful API work with Java and the Spring Framework.
• MSA-based system development and operations experience.
• RDBMS design and SQL authoring / tuning ability.
• Track record of running stable services under high-traffic load.
• Comfort working with AI coding agents and a habit of verifying AI output.
• Business-level English (working language).
• Spring Boot 4.x / Java 21 / JPA / Flyway or equivalent modern stack.
• CQRS, DDD, event-driven architecture design and operations.
• AWS (ECS Fargate, ElastiCache, RDS, S3) operations.
• Payments / settlement, E-commerce, O2O, or hotel & travel domain experience.
• Hands-on with AI coding agents (Claude Code, Cursor, Copilot, etc.).
• LLM API / RAG / agent-driven feature development or workflow automation.
• Korean or Vietnamese language ability (a plus for collaboration with Seoul HQ and the Vietnam branch office)
• Tech stack
• Java 21 - Spring Boot 4.x - Gradle - CQRS - JPA + Flyway - PostgreSQL - JUnit 5 (Strict TDD) - Elasticsearch - AWS (ECS Fargate, RDS, S3) - Structured logging + distributed tracing
• Working environment
• Direct CTO Office reporting - Tech Lead in the same team; fast technical decisions and release cycles.
• Full AI agent adoption - Claude Code licensed in-house plus our public Claude Code plugin suite hare-cc-plugins. One step beyond "using AI" - we design and operate it.
• AX beyond engineering - autonomous workflow agents are rolling out in marketing, sales, and strategy. The whole company is moving in the same direction.
• Front line of AI engineering - prompt → context → harness engineering, learned hands-on in the OTA industry. You build the skills that will be standard for senior engineers 1-2 years from now.
• Fact-based documentation culture - assert only what is verified by code, schema, or data; label assumptions as assumptions.
• Global collaboration - joint work with 11 engineers in our Vietnam branch office.
• How to apply
• Email: cto.office@ohmyhotel.com or hr.sg@ohmyhotel.com
• Location: Singapore
• Submit: CV, work-experience summary, and (optional) portfolio / GitHub / tech blog

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