Senior Backend Engineer (Node.js/TypeScript)

We are looking for a Senior Backend Engineer (Node.js/TypeScript) – Data & Search for one of our clients within Banking & Finance.

Start date: 2026-09-11
End date: 2027-06-30
Location: Stockholm

About the assignment:
You will join a team building a high-performance API that serves static and market data for financial instruments across retail investment channels. The platform is powered by OpenSearch as both data store and search engine, handling complex queries, ranking, and aggregations at low latency. Daily releases and TDD are core to the team's workflow.

Core Responsibilities:

• Design and optimize OpenSearch queries, indexing strategies, aggregations, and ranking logic for low-latency, high-scale workloads
• Build and maintain data ingestion pipelines that compile and normalize data from multiple external sources
• Develop and extend the backend API using Node.js and TypeScript with a focus on customer value and testability
• Apply TDD practices including unit and end-to-end tests to ensure reliable daily releases

Profile & Qualifications:

• Senior-level backend engineer with extensive hands-on experience in data-intensive systems and search platforms
• Strong understanding of financial instruments, markets, and financial analysis is highly valued
• Experience working in agile teams with continuous delivery practices
• Self-sufficient and customer-focused mindset with ability to collaborate across disciplines

• Node.js
• TypeScript
• OpenSearch or Elasticsearch (advanced: indexing, query design, aggregations, ranking, performance tuning)

• Self-hosting and operating OpenSearch/Elasticsearch clusters
• TDD
• Data ingestion and reconciliation pipelines
• Financial domain knowledge