Backend Engineer – Payments Platform (Java/Kotlin, AWS)

United States Digital Space LLC; Greater London; On-site; GBP 70,000 - 100,000; Full time

Job summary

Wiser in London is seeking a backend engineer to help build the Direct Debit/API powered platform. You will design, test, and maintain backend services in Java and Kotlin using Spring Boot, deployed on AWS, serving millions of customers.

You will work on RESTful APIs, data schemas in PostgreSQL, event-driven architectures with Apache Kafka, and a payment orchestration system to optimize costs and reliability. Strong focus on security and reliability.

Qualifications

• Proficient in Java/Kotlin with Spring Boot
• Experience designing RESTful APIs and cloud deployments
• Strong knowledge of PostgreSQL and SQL optimization
• Experience with Kafka-based event-driven architectures
• Familiarity with payment platforms and security best practices

Responsibilities

• Design, develop, test, and maintain backend services written in Java and Kotlin using the Spring Boot framework, deployed on cloud infrastructure (AWS)
• Build and maintain RESTful APIs that serve millions of customers across web and mobile platforms
• Develop and optimise services powering the card pay‑in payment method — one of the most popular payment methods, enabling the company customers to move around £1 billion every month
• Design and implement database schemas, write and optimise SQL queries against PostgreSQL databases handling high‑volume transactional data
• Build and maintain event‑driven architectures using Apache Kafka for asynchronous processing of financial events across distributed services
• Develop and maintain a payment orchestration system that dynamically routes payments across Payment Service Providers to optimise for cost and reliability
• Write automated tests (unit, integration, and end‑to‑end) to ensure correctness and reliability of financial systems
• Conduct code reviews for team members, ensuring code quality, security, and adherence to engineering standards
• Participate in on‑call rotations to monitor and respond to production incidents for Tier 2 critical services
• Collaborate with product managers, designers, analysts, and engineers across other teams to deliver cross‑functional projects
• Identify and resolve performance bottlenecks, scalability issues, and technical debt in existing systems
• Ensure development follows security best practices, particularly around handling of sensitive financial data and compliance with financial regulations

Skills

Java

Kotlin

Spring Boot

RESTful APIs

AWS

PostgreSQL

Kafka

Tools

PostgreSQL

Kafka

AWS

Job description

Wiser in London is seeking a backend engineer to help build the Direct Debit/API powered platform. You will design, test, and maintain backend services in Java and Kotlin using Spring Boot, deployed on AWS, serving millions of customers.

You will work on RESTful APIs, data schemas in PostgreSQL, event-driven architectures with Apache Kafka, and a payment orchestration system to optimize costs and reliability. Strong focus on security and reliability.