Contract Senior Java Developer - Data

Quant Capital
London

Contract Senior Java Developer – Data

Up to £700 per day Outside IR35 (6 month rolling)

In office – City of London

Quant Capital is hiring for a small, high-performing market maker in London. This is a junior-to-mid role focused primarily on Java development, with a secondary responsibility owning straightforward Python ETL/data ingestion into AWS and PostgreSQL. This is a growing team focused on data ingestion and building tooling for the wider firm.

What you’ll do:

  • Build and enhance Java backend services (APIs, batch jobs, integrations) used across the business
  • Write clean, testable code with solid engineering discipline (testing, code review, debugging, production support)
  • Maintain and extend Python-based ingestion/ETL (pragmatic plumbing, not heavy data engineering)
  • Work with PostgreSQL (schemas, migrations, performant queries, data validation)
  • Improve service reliability: monitoring/logging, sensible alerting, and predictable deployments via CI/CD

Tech:

Java (primary), Python (secondary), AWS, PostgreSQL + Git, CI/CD, logging/monitoring

What they want:

  • 10+ years of experience building production systems (or equivalent ability)
  • Strong Java fundamentals (OO design, APIs/services, concurrency basics, testing)
  • Some UI development
  • Comfortable with SQL/PostgreSQL
  • Some Python experience (enough to manage and improve existing ETL/ingestion)

Nice to have

  • Any finance or markets exposure
  • Familiarity with common AWS patterns for running services and pipelines

Why this role

  • Broader scope than pure app dev: you’ll understand the data feeding the platform
  • Lean team, high impact, strong growth runway
Posted 2026-03-12

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