Senior Full Stack Engineer

Location: Remote, EU/UK preferred
Team: Engineering
Type: Full-time contractor

We are looking for a Senior Full Stack Engineer to join a small, high-impact engineering team. You will work across the product surface: React front end, NestJS backend, durable execution system, Postgres data layer and proprietary systems for evaluating and managing systems of LLMs. Some of this you may not have done before, but you will apply your transferable skills and experience!

This role suits someone who enjoys a variety of challenges, extending the forefront of what it takes to deliver reliable and trustworthy AI systems, and making those things simple and a joy to use. You will understand product needs, design clean domain models, build reliable components, ship easy-to-use interfaces, and debug distributed execution behaviour when things get interesting.

What You’ll Work On

Build product features across our React/Vite frontend, NestJS backend, PostgreSQL data layer, and Temporal-powered worker stack.
Develop new ways to benchmark and optimise LLM use, including error detection and correction and blocking AI-focused security attacks
Identify where AI can meaningfully improve structured tasks (and not make things worse): extraction, classification, decision support, agentic tool use, document understanding, communication handling, and automation of tedious operational steps.
Design and extend systems to proactively benchmark, monitor, manage and optimise LLM selection, quantify drift in production, and measure cost vs. performance
Build APIs, data models, and tenant-aware authorization boundaries for workflows, executions, agents, connectors, inbox, dashboards, and configuration.
Create polished interfaces for workflow authoring, execution monitoring, review queues, dashboards, and configuration-heavy SaaS workflows.
Improve reliability through strong testing, runtime visibility, replay-safe changes, and careful debugging across UI, API, database, workers, and external services.

Who We’re Looking For

Required Experience

8+ years of professional software engineering experience, with strong ownership of production enterprise systems.
React experience, especially building complex data-heavy product interfaces
Experience with multi-tenant, distributed back-ends with mandatory authentication/authorization
Solid PostgreSQL experience, including schema design, migrations, query performance, transactional thinking, and gated data access.
Experience with durable or asynchronous systems: workflow engines, queues, jobs, event-driven systems, state machines, distributed orchestration.
Comfort debugging complex production behaviour across UI, backend, database, workers, and third-party integration layers.
Strong testing discipline and the ability to choose the right level of test for the risk involved.

Advantageous to have

Temporal.io experience, or comparable experience with durable workflows and replay-safe execution models.
Experience designing or maintaining workflow builders, automation platforms, rules engines, low-code tools, or developer-facing DSLs.
Experience identifying practical AI use cases inside business processes, especially where LLMs complement deterministic workflow logic.
Experience with AI/LLM integrations in production, including OpenAI, Anthropic, Gemini, structured outputs, tool use, agent patterns, or provider abstraction.
Experience with security-sensitive backend work: RLS, secure credential storage and tenant isolation
Experience with Kubernetes, Terraform, or other distributed orchestration systems

Core Competencies

Systems thinking: You can reason about frontend state, API contracts, database state, background execution, and external systems as one product.
Product-minded engineering: You care whether a feature meets the product requirements and is also understandable, simple to use, and operationally reliable
Autonomy and ownership: You can take a loosely defined problem, collaborate to discover the constraints, make good tradeoffs, and ship.
Clear communication: You can explain tradeoffs, document decisions, and collaborate well with product, design, AI, and engineering teammates.
Accountability and integrity: You take responsibility for outcomes, communicate transparently, and uphold high standards in both technical and team-impacting decisions.

Why Join

You’ll be joining a small, global team building a technically ambitious product at a stage where senior engineers can have a real impact.

Senior Full Stack Engineer at Aguru UK Ltd