Principal Java Software Engineer in London

Mangopay is a wallet‑based payment infrastructure built specifically for organisations with complex, multi‑party fund flows. A pioneer in multi‑party payments.

Our solution optimises fund flows on behalf of the organisations we work with using wallets as programmable, composable building blocks.

Mangopay’s regulated platform collects payments, secures transactions and holds funds, splits money between the various parties in the funds flow, and ultimately manages the payout to service providers, sellers, and consumers.

Platforms and fintechs using Mangopay regain control and transparency over multi‑party payment flows , generate additional revenue, and improve operational efficiency. They can stay compliant while innovating and scaling.

Job Description

As a principal software engineer you will be part of one of our scrum teams and lead the future architecture and development for the team.

We are seeking an experienced Principal Engineer to provide technical expertise in a distributed, highly available application, where system quality and performance is critical.

This is a high‑impact, hands‑on Individual Contributor (IC) role focused on technical excellence and architectural leadership, not people management.

You will write code, set standards, and raise the engineering bar across the organization.

Responsibilities

• Drive day‑to‑day development activities by leading architectural decisions, designing robust systems, and conducting rigorous design and code reviews.
• Ensure consistent implementation against existing architectural principles while proactively defining new standards to future‑prove our ecosystem.
• Work closely with software engineers, principal engineers, architects and product managers to break down complex problems into clean, deliverable value.
• Guarantee the team adheres to world‑class best practices for system monitoring, alerting, and proactive failure detection.
• Partner with the Engineering Manager to identify, propose, and implement strategic technical and organizational improvements within the team.

Qualifications

• You have 7+ years as a Backend developer using Java (Java 11 through Java 21+).
• You have experience leading and mentoring backend engineers, providing guidance and direction on best practices and technical decisions.
• You have experience building high‑throughput, low‑latency products, ideally within the fintech, banking, or payments industry.
• You have experience in developing software using Micronaut or another cloud native framework (Spring Cloud) in large‑scale production systems.
• You are comfortable working in a modern cloud architecture using AWS or another cloud environment.
• You have deep experience designing, building, and troubleshooting highly scalable, event‑driven systems using Kafka, Rabbit MQ, or similar distributed messaging frameworks.
• You have the ability to create unit tests and functional with JUnit 5 or Spock.
• You are an advocate software engineer learning and growth‑focused mindset and a strong desire to share your skills and learn from those around you.
• You have experience leveraging AI‑assisted development tools (e. g., Claude Code, Cursor, Codex, LLMs) to accelerate workflow efficiency, optimize code quality, and guide the team on modern development practices is highly valued.
• In the first month, you'll
• Become an expert on Echo’s core APIs, identifying quick wins for immediate architectural or performance improvements.
• Deep‑ dive into Mangopay’s global architecture, understanding how the Echo team interacts with the broader Payments Universe.
• Develop your first tasks ensuring consistent implementation against existing architecture principles as well as improve and define new principles.
• Within the first 3 months, you'll
• Gain full autonomy within our event‑driven architecture.
• Take end‑to‑end ownership of a major technical epic, guiding it from design doc to production.
• Partner tightly with Product and QA to ensure seamless acceptance criteria and zero‑downtime deployments.
• Within the first 6 months, you'll
• Take a hands‑on role in influencing and guiding day‑to‑day development activities by leading architecture decisions, participating in designs, design review, code review, and implementation.
• Work with the engineering manager to propose and implement technical and/or organizational improvements in the team.
• Within the first 12 months, you'll
• Potential to be part of the hiring process and mentor the next software engineer(s).
• Have the ability to lead an entire new project transforming product requirements into technical implementation descriptions, take ownership and be responsible to deliver into production.
• What we do in Echo
• Maintain and improve with new features the product.
• We design, maintain, and optimise systems capable of handling massive volumes of concurrent traffic and peak transaction spikes.
• We rapidly build and integrate sophisticated new fintech features or payment flows without compromising on system reliability or backwards compatibility.
• Recruitment process
• HR call (30 min)
• 1st interview with Software Engineer Manager
• Technical interview with Senior Software Engineer
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