Software Engineer: Platform and Backend (Mid-career / Senior)

As an engineer on the Platform team you’ll productise our data and build the ways customers access and work with it. You’ll own the analytical services, APIs and MCP connectors that let customers query our data directly from the tools they already use, and build first-party applications powered by our data. What you’ll do

• Build and operate async REST endpoints (FastAPI, Pydantic) that serve large datasets reliably and quickly.
• Work with large tabular data in pandas, Parquet/Arrow and DuckDB, and manage the memory and performance trade-offs of moving big datasets efficiently.
• Own the identity and access layer, including AWS technologies for identity, authorisation and data distribution, supporting access to data through multiple channels.
• Design and build new access points for our data, such as APIs, analytical services and MCP connectors.
• Run services on AWS, with infrastructure in AWS CDK shipped via CodePipeline.
• Productionise code from the data and quantitative teams.
• Occasionally contribute changes to Theia Insights’ TypeScript/React frontends that consume our API, particularly where a feature is simplest to own end to end.
• Take end-to-end ownership of reliability and performance, including graceful handling of failure modes.

• Strong production Python including experience shipping and operating services.
• HTTP APIs in a typed framework such as FastAPI, with schema and contract discipline.
• Production AWS: S3, a compute service (e.g. ECS/Fargate or Lambda) and a datastore, with least-privilege IAM.

Useful

• Auth in production: OAuth2/OIDC, JWT validation, API keys, scopes.
• Tabular data at scale: pandas plus Parquet/Arrow, ideally DuckDB.
• Multi-tenant SaaS: RBAC, API-key management.

Nice to have

• Infrastructure as code (CDK in TypeScript, or Terraform).
• React/TypeScript, or comfort in a polyglot repo.
• LLM or MCP integration and AI-facing tooling.
• Financial-data or regulated-environment background.

Experience we’re looking for

We care more about what you’ve owned than years on a CV. A strong mid-level engineer who has shipped and operated production AWS services, owning one end to end with tests, will meet the bar. Senior candidates will likely have designed large scale systems, owned responsibilities for auth or multi-tenant access, made cross-region and disaster-recovery trade-offs, and set the standard for a team.

• Competitive salary plus EMI share options
• 25 days holiday + bank holidays
• Private health insurance, pension
• Hybrid working in UK from London or Cambridge

Theia Insights builds foundational financial intelligence products, including industry classification, knowledge graphs and factor risk models, for institutional investors. We serve some of the largest asset managers, hedge funds, index providers and sell-side banks.