Contract Senior Java Developer – Data/Marketmaking

Contract Senior Java Developer – Data/Marketmaking

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 si 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