About StackOne
StackOne is the AI Integration Gateway powering the next generation of SaaS and AI Agents. Backed by GV, Workday Ventures, and angels/advisors from DeepMind, OpenAI, GitHub, and Mistral, we’ve raised $24M to enable developers to orchestrate thousands of secure, scalable, and accurate actions in AI Agents.
With an AI-native integration toolkit that delivers real-time execution, managed authentication, granular permissions, and full observability—built with safety at its core—we’re now doubling down on AI R&D and creating our own lab to push the boundaries of tool calling for agents: training specialized LLMs designed to outperform general‑purpose models in what matters most: precision, reliability, and safety in agentic execution.
About The Role
We’re looking for full‑stack engineers who can ship fast, think in systems, and obsess over scalability, performance & usability. You’ll build core APIs, scale infra, and ship dev tools & UIs that make tool execution easy, safe and predictable.
It’s a broad role: backend‑heavy, product‑aware, and deeply technical. Expect to work across APIs, auth, infra, and frontend, building the foundation that lets agents take real action.
Responsibilities
- Act as a full‑stack web application engineer: ideate, build, and ship features across frontend, backend, data, and infrastructure.
- Model data & schemas across SQL, document/columnar stores, and OLAP; design for correctness, performance, and cost.
- Design and evolve public APIs and standards: REST contracts, OpenAPI, pagination, auth, error models, plus MCP/tool‑calling conventions.
- Engineer for scale and resilience: rate limiting, retries, idempotency, back‑pressure, caching, SLIs/SLOs, and safe fallbacks.
- Build and operate event systems with Kafka‑class streaming patterns: producers/consumers, partitioning, DLQs, reprocessing, schema evolution.
- Raise observability & reliability: tracing, metrics, logs, alerting, zero‑downtime deploys, runbooks.
- Leverage LLMs/agents to accelerate development while maintaining reliability, testing, and code quality.
What We're Looking For
- Proven experience as a full‑stack engineer shipping user‑facing, backend‑heavy systems.
- Expertise in TypeScript and solid experience with React; comfortable building clean UIs for complex backend capabilities.
- Strong background designing and operating public APIs and multi‑tenant systems.
- Experience with distributed systems concepts: streams, queues, idempotency, consistency, and performance trade‑offs.
- Ability to think in systems (throughput, tail latency, failure modes) and explain trade‑offs clearly.
- Curiosity and pragmatism with LLMs/agents: know when they help, and how to guardrail/evaluate them.
- Desire to work in a fast‑paced startup, take ownership end‑to‑end, and bias toward shipping.
- (Preferred) Experience publishing CLIs & SDKs (internal or open‑source).
Our Stack
You will have a lot of freedom and agency to choose and work with the technologies you love. Our tech stack includes:
- Infra & monitoring: AWS (ECS, RDS, Elasticache, Lambda, etc.), Cloudflare, Tinybird, Modal, Dagster, Langsmith, Datadog, Sentry, Incident.io
- Languages & frameworks: TypeScript (Node.js), Python, NestJS, React, Svelte
- Other day‑to‑day tools: Postman, Notion, Slack, Jira, GitHub and more
Benefits
- 25 days holiday + 1 additional day holiday per year of tenure
- Participation in the company’s employee share options plan
- Private health insurance (including dental & optical)
- Health, fitness and gift card discounts
- £1,000 for your home office set up + £500/year top‑up
- Paid lunch in the office
- Annual team offsite to sunny spots (last ones were in Spain and Portugal)
- Join one of Europe’s fastest‑growing startups
- Work with a veteran team of ex‑employees of Google, Microsoft, Oracle, Coinbase, JP Morgan and more
- Cycle2Work and Electric Cars scheme
- Hybrid work set up – typically 2 days in the office
We believe diversity drives innovation. We encourage individuals from all backgrounds to apply. As an equal‑opportunity employer, we celebrate diversity and are committed to creating an inclusive environment for all employees.
Compensation Range: £65K – £100K
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