About StackOne

StackOne is the universal integration gateway for modern SaaS products and agents. We’ve raised $24m in 2 years, and we’re backed by top tier investors like Google Ventures and Workday Ventures.

StackOne sits behind the scenes as the integration layer providing thousands of tools,: SOC 2 compliant, multi-tenant, and invisible to end users powering integrations for future-of-work SaaS categories such as HR, Compliance, and AI Agents.

Our customers are established B2B SaaS companies or small to enterprise companies building Agents to sell or to improve their own processes.

About the role

We're building a world where users of any SaaS can integrate with the tool of their choice in one click thanks to StackOne. We're convinced AI is pivotal to making this a reality by transforming how SaaS talks to each other and this is what you will help achieve.

We are looking for a Software Engineer with a strong background in AI production-grade applications with professional experience working with LLMs (eg: GPT, Anthropic and others).

In this role, you will deliver AI features and products end-to-end and work with the wider AI team of StackOne (comprising of AI researchers and other AI engineers). You will report directly to the CTO.

Responsibilities

• Act as a full-stack web application engineering: 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 chose 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 2d in the office

Ready to help us change the game for SaaS integrations? Get in touch and let's chat!

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.