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

Theia Insights; Greater London; Hybrid; GBP 75,000 - 110,000; Full time

Benefits offered by this job

EMI share options

25 days holiday + bank holidays

Private health insurance

Pension

Job summary

Theia Insights is building foundational financial intelligence products for institutional investors. This role focuses on producing reliable, scalable REST endpoints (FastAPI) and managing access to large datasets using Pandas, Parquet/Arrow and DuckDB.

You’ll own the identity layer (OAuth2, JWT, API keys) in a multi-tenant SaaS setup on AWS and contribute to data-facing services and occasional frontend work.

Qualifications

• Production-level Python development and operation experience.
• Experience shipping HTTP APIs with typed frameworks (e.g., FastAPI).
• Strong AWS experience with IAM, data services and least-privilege access.
• Experience with RBAC, multi-tenant SaaS architectures.
• Familiarity with data formats and analytics stacks (Parquet/Arrow, DuckDB, Pandas).

Responsibilities

• Build and operate async REST endpoints using FastAPI and Pydantic.
• Handle large datasets with Pandas, Parquet/Arrow and DuckDB.
• Own identity and access layer with AWS IAM, OAuth2/OIDC and API keys.
• Design APIs and data access points for analytics and MCP connectors.
• Run services on AWS (CDK, CodePipeline) and ensure reliability.
• Contribute to frontend TypeScript/React components when needed.
• Ensure end-to-end reliability and graceful failure modes.

Skills

Python production

FastAPI

OAuth2/OIDC

RBAC

JWT

API keys

Multi-tenant

Terraform

CDK

TypeScript

React

Tools

Pandas

Parquet/Arrow

DuckDB

AWS CDK

CodePipeline

S3

ECS/Fargate

Lambda

Job description

About the role

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.

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.
  Essential
• 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