Senior Java Developer – Data

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/CDTech:

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/PostgreSQLSome 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