Senior Backend Engineer - Java/Architecture
Senior Backend Engineer (Java / Architecture)
Watu · Technology Organisation · Reports to Tech Lead
Location
Europe
Reports to
Tech Lead of assigned squad
Primary language
Java (Spring Boot) - architecture depth and system design expected, not Java-only focus
Seniority
Senior - 5+ years
About Watu
Watu is a fintech company operating across Africa and Latin America, providing device financing and financial services to customers historically excluded from the formal financial system. We finance motorcycles, smartphones and other productive assets through a technology-first, data-driven approach - enabling customers to own income-generating assets and build credit histories.
Our platform supports millions of customer journeys across Kenya, Uganda, Tanzania, Ivory Coast, Ghana, and beyond, with continued expansion into LATAM.
The Role
Senior Backend Engineer at Watu means owning a domain end-to-end inside your squad - and influencing how that domain evolves. You write code, but you also shape the system. You bring architectural opinions that the Tech Lead can rely on, you raise the quality bar for the engineers around you, and you take full responsibility for the reliability and maintainability of what you build.
We use Java as our primary backend language, but we do not hire Java developers who only think about Java. We hire engineers who happen to use Java. The difference matters: we want people who can reason about distributed systems, design clean APIs, think about failure modes before they happen, and care about the downstream consumer of their code as much as the implementation.
You will be embedded in a squad of 4–6 people. Your Tech Lead is your primary technical counterpart and reviewer, but at the senior level the expectation is that you operate with significant autonomy. You are not waiting to be told what to build or how to solve a problem - you bring a point of view, surface design decisions proactively, and contribute to the direction of your domain.
What You Will Do
- Design, build, and maintain backend services and APIs consumed by other squads, external partners, and customer-facing products.
- Write unit and integration tests as a first-class part of development - not as a separate phase, not as something the QA engineer handles for you.
- Drive architecture discussions within your squad - propose designs, write Architectural Decision Records, and defend technical choices clearly. At the senior level you are an active contributor to how the system evolves, not just an implementer of decisions made by others.
- Review pull requests with depth and directness. Your reviews go beyond correctness - you assess design, maintainability, performance, and test coverage. You are a quality benchmark for the squad, and your reviews make engineers better.
- Write and maintain technical documentation: API specs (OpenAPI), service READMEs, runbooks for systems you own. If you built it, you document it.
- Contribute to shared libraries and platform standards when your work has cross-squad value.
- Use AI/LLM tooling actively in your workflow - code generation, test writing, debugging, documentation. We expect this, not just permit it.
Who You Are
Technical - essential
- 5+ years of professional backend software engineering experience, with at least 3 years working in Java in a production environment at a level where you were making design decisions, not just implementing them.
- Java and Spring Boot depth - you understand the framework, not just its syntax. Dependency injection, Spring Security, Spring Data, transaction management, and testing with Spring Test are all familiar territory.
- REST API design - you know what makes a good API (versioning, error handling, idempotency, pagination) and you design accordingly, not just implement to spec.
- Relational database design - schema design, indexing, query optimisation, and understanding the performance implications of your data model cho