Principal Product Engineer

Diesta Limited; Greater London; Hybrid; GBP 110,000 - 150,000; Full time

Benefits offered by this job

Hybrid work model

London office access

Team lunches and offsites

State-of-the-art equipment

22 days annual leave

Job summary

Diesta Limited in London seeks a Principal Backend Engineer to lead the technical evolution of our backend platform. This deeply technical role demands architectural judgment, setting a high engineering bar and helping the team scale a complex, data-intensive system with confidence.

You will own the technical direction across NestJS, Node.js, TypeScript and AWS, design well-typed APIs, enforce clear boundaries, and ensure observable, recoverable operations.

Qualifications

• Experience designing and evolving production backend platforms.
• Deep knowledge of NestJS, Node.js and TypeScript including modular architecture and testing.
• Operational considerations: observability, reliability, and performance.

Responsibilities

• Lead backend technical direction and architectural choices.
• Evolve a modular NestJS architecture with clear module boundaries.
• Design well-typed APIs and integration contracts.
• Scale data architecture for high-volume workloads.
• Maintain data layer and application boundaries for clarity.
• Model reversible actions and downstream propagation.
• Improve observability, incident response and recovery.
• Lead design reviews and mentor engineers.

Tools

AWS

Docker

MySQL

Job description

We are seeking a Principal Backend Engineer to lead the technical evolution of Diesta’s backend platform. This is a deeply technical role for someone who can make difficult architectural decisions, set a high engineering bar and help the team scale a complex, data-intensive system with confidence.

You will own technical direction across our NestJS, Node.js, TypeScript and AWS backend: designing well-typed APIs, clear service and data boundaries, robust processing workflows and platform capabilities that can handle millions of records and events without compromising correctness, observability or operability.

A key part of the role is separating the data layer from the application layer. You will help ensure an action taken in the Portal has an explicit, reversible application-level meaning, while durable downstream processing and propagation are modelled independently, safely and transparently.

This role is not primarily about product discovery or customer-problem framing, although product understanding is a strong advantage. Your main focus is technical excellence: making the system more scalable, reliable, comprehensible and easier for the engineering team to evolve.

As Diesta moves from an AI-driven SDLC towards a more agentic one, you will use AI-assisted tools to increase technical leverage, improve engineering workflows and raise the quality of design, code review, testing and documentation - always with rigorous human judgement.

Key Responsibilities

Technical Direction: Lead the backend technical effort, establish architectural direction, and guide the team through complex design choices, refactoring priorities and engineering trade-offs.

NestJS Architecture: Design and evolve a clean, modular NestJS architecture with clear module boundaries, dependency management, testability and maintainable conventions.

Typed APIs and Contracts: Design well-typed, version-aware APIs and integration contracts that are clear to consumers, resilient to change and straightforward to test and observe.

Scalable Data Architecture: Design data and processing patterns for high-volume workloads, including millions of records or events, with attention to performance, consistency, resilience and operational cost.

Layering and Boundaries: Maintain a clear separation between the data layer, domain/application logic and delivery layer so that system behaviour remains comprehensible and change is controlled.

Reversibility and Propagation: Model Portal actions, state transitions, undo paths and downstream propagation separately, ensuring that customer-facing actions can be reversed safely without creating hidden inconsistency underneath.

Reliability Engineering: Improve idempotency, retry behaviour, failure isolation, observability, alerting and recovery across critical workflows and integrations.

Technical Leadership: Lead design reviews, mentor through code review and pairing, make technical standards explicit, and help engineers grow their ability to work effectively in a complex system.

System Improvement: Identify and drive pragmatic improvements to scalability, maintainability, security and operational robustness, working with the existing team that built and knows the platform.

AI-Assisted Engineering: Use AI tools and agentic workflows to accelerate codebase analysis, implementation planning, testing, documentation and technical investigations, while improving the repeatability of engineering work.

Collaboration: Work closely with backend and frontend engineers, QA, DevOps, data engineers and engineering leadership to turn technical direction into durable delivery.

Documentation: Produce clear architectural decision records, API and data-contract documentation, and operational guidance that humans and AI agents can use safely.

What We’re Looking For

Principal-Level Backend Experience: Substantial experience designing and evolving production backend platforms, with a track record of technical leadership in complex, high-scale systems.

NestJS and TypeScript Depth: Deep practical knowledge of NestJS, Node.js and TypeScript, including modular architecture, dependency injection, validation, testing and production operations.

Infrastructure and Databases: Strong production experience with AWS, Docker and MySQL or another comparable relational database, including operational, performance and reliability considerations.

API Design: Strong experience creating well-typed APIs and integration contracts, with sound judgement around versioning, compatibility, validation, error handling and security.

Data and Scale: Demonstrable experience with high-volume data processing, distributed or event-driven workflows, MySQL or comparable relational databases and the trade-offs required to keep systems reliable at scale.

Architecture: Exceptional ability to define clear boundaries, reason about coupling and failure modes, and make systems easier to understand, change and operate.

Operational Excellence: Strong experience with observability, incident investigation, performance analysis and designing for recovery and resilience.

Technical Leadership: Ability to lead through influence: articulate a technical direction, make sound decisions, improve standards and enable a team without needing formal people management.

Engineering Judgement: Ability to balance long-term quality with pragmatic delivery, and to explain technical choices clearly to engineers and engineering leadership.

AI-Native Mindset: Comfortable using AI tools to increase engineering leverage while reviewing outputs critically, protecting quality and improving repeatable technical workflows.

Useful but not required

Experience or interest in any of the following would be helpful:

Event-driven architectures, messaging, queues, outbox patterns or workflow orchestration

Financial systems, payments, insurance, insurtech, fintech or other regulated data environments

Migration and modernisation of systems with live customer and operational dependencies

Security, compliance, auditability, access control and data-retention concerns

Performance engineering, load testing and cost-aware infrastructure design

Angular or other frontend experience, and product thinking - valuable, but not central to the role

AI-assisted internal tooling, agent workflows or developer productivity systems

A visible record of open-source contribution, technical writing, public talks or other thoughtful public technical work

Join a mission-driven team addressing real pain points in insurance finance.

Be part of a lean, high-performing team with direct impact on product and client outcomes.

Work with top insurers and brokers in an industry ripe for disruption.

A culture of high trust, low ego: we value competence, commitment and transparency.

Hybrid work model with a central London office (Bank / Liverpool Street).

Regular team lunches and international offsites.

State-of-the-art technical equipment.

22 days annual leave (excluding bank holidays).

Interview Process

Intro Call with our Chief of Staff to explore your background and aspirations.

Technical Architecture Interview with the Head of Engineering, focusing on backend architecture, scale and systems design.

Onsite Workshop at our London office, discussing a technical problem with the team and experiencing our culture first-hand.

Interested in solving real-world data problems and shaping the future of insurance payments?

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Diesta Limited (Company Number: 13969906, Firm Reference Number: 1012426) is an agent of Plaid Financial Ltd. (Company Number: 11103959, Firm Reference Number: 804718), an authorised payment institution regulated by the Financial Conduct Authority under the Payment Services Regulations 2017. Plaid provides you with regulated account information services through Diesta as its agent.