Lead Backend Engineer

OnArrival is building the core infrastructure layer for travel - powering flights, hotels, insurance, payments, and post-booking systems for large platforms. We operate where:

• APIs are unreliable
• Failures cost money
• Scale is not optional

What You'll Do

• Architect and build backend systems using Spring Boot + Kotlin/Java
• Own platform-critical systems:
• Booking lifecycle
• Payments, refunds, reconciliation
• Supplier orchestration (GDS, aggregators)
• Design for:
• Failures, retries, idempotency

High concurrency and race conditions

• Build event-driven systems
• Lead engineers via:
• Code reviews (non-negotiable)
• Architecture decisions
• Mentorship

Required Technical Skills (Non-Negotiable)Core Backend

Strong hands-on experience with:

• Java (8+) and/or Kotlin
• Spring Boot (deep understanding, not just usage)
• Solid grasp of:
• Multithreading & concurrency
• JVM internals (memory, GC basics, performance tuning)
• Ability to design:
• Clean, modular, scalable architectures

System Design & Distributed Systems

Strong experience in:

• Designing distributed systems
• Handling partial failures
• Building fault-tolerant services
• Must understand:
• Idempotency
• Circuit breakers, retries, backoff strategies
• Eventual consistency
• API rate limiting and throttling

APIs & Integrations

Experience building and consuming:

• REST APIs (well-designed, versioned)
• Experience handling:
• Third-party APIs with:
• Timeouts
• Inconsistent schemas
• Failure scenarios
• Ability to design:
• Resilient integration layers

Databases

Strong experience with:

• MongoDB (or other NoSQL DBs)
• Postgres (or any relational DB)
• Must understand:
• Data modeling (NoSQL vs relational trade-offs)
• Indexing strategies
• Query optimization
• Transactions and consistency models

Event-Driven Architecture

Hands-on experience with:

• Kafka (or similar message brokers)
• Must understand:
• Producers/consumers
• Consumer groups
• Message ordering and delivery guarantees
• Dead-letter queues, retries

Scalability & Performance

Experience with:

• High-throughput systems
• Low-latency APIs
• Ability to:
• Identify bottlenecks
• Optimize performance (DB, APIs, memory, CPU)

Observability & Debugging

Experience with:

• Logging, monitoring, alerting systems
• Ability to:
• Debug production issues
• Trace distributed system failures

Cloud & DevOps (Working Knowledge Required)

Familiarity with:

• AWS (or any cloud platform)
• Containerization (Docker)
• Understanding of:
• CI/CD pipelines
• Deployment strategies

Code Quality & Engineering Practices

Strong emphasis on:

• Code reviews (you will both give and receive)
• Writing clean, maintainable code
• Testing (unit/integration)
• Experience with:
• Git workflows (branching strategies, PR reviews)

Nice to Have (But Valuable)

• Travel domain experience (GDS, booking systems)
• Payments / fintech systems
• Elasticsearch, ClickHouse
• High-scale reconciliation systems

What This Role Actually Means

• You own systems where bugs = real money loss
• You design for failure before success
• You dont ship fragile systems

What Will NOT Work Here

• Low ownership mindset
• Avoiding production responsibility
• Over-indexing on titles
• Weak fundamentals hidden behind frameworks

What You Get

• Real ownership
• Real scale
• Real impact