Contract Senior Java Developer - Data/Marketmaking

Contract Senior Java Developer - Data/MarketmakingOutside IR35 (6 month rolling) In office - City of LondonQuant 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 businessWrite 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/monitoringWhat they want:10+ years of experience building production systems (or equivalent ability)Strong Java fundamentals (OO design, APIs/services, concurrency basics, testing)Some UI developmentComfortable with SQL/PostgreSQLSome Python experience (enough to manage and improve existing ETL/ingestion)Nice to haveAny finance or markets exposureFamiliarity with common AWS patterns for running services and pipelinesWhy this roleBroader scope than pure app dev: you’ll understand the data feeding the platformLean team, high impact, strong growth runway