Backend engineer for data pipelines

We're looking for a skilled Mid-Level Data Engineer for one of our clients (TOP Startup) to design, build, and optimize data pipelines and backend services that ensure clean, reliable data across the organization. As a Mid-Level Backend Engineer on our Tech Team, you will design, build, and optimize the data pipelines and backend services that keep clean, reliable data flowing across the entire organization. You will own the full lifecycle of data ingestion and transformation work — from understanding a business requirement through to production deployment — and directly shape the backend infrastructure that powers our data-driven decision-making at Flanks.

• Design, develop, and maintain scalable ETL/ELT pipelines to ingest, transform, and load data from multiple disparate sources into our core systems.
• Write clean, efficient Python code with a strong focus on performance — applying optimal data structures and algorithms to handle high-volume datasets reliably.
• Collaborate on database schema design (SQL and NoSQL) and own query performance optimization to ensure fast, accurate data access.
• Implement unit tests, integration tests, and data quality checks to guarantee pipeline integrity and catch issues before they reach production.
• Deploy and iterate on pipelines using CI/CD practices and containerization tools such as Docker, participating actively in code reviews to uphold team standards.

• Strong Python and/or JavaScript/NodeJS engineering skills with a focus on performance, memory efficiency, and writing maintainable, production-grade code.
• Solid experience building and operating data pipelines — ETL/ELT patterns, pipeline orchestration, and handling large-scale data ingestion — or experience building backend services for a product, ideally with exposure to Elasticsearch.
• Familiarity with both SQL and NoSQL databases, including schema design and query optimization.
• Comfort working autonomously — able to take a high-level requirement, define scope, and drive it to production without heavy hand-holding.
• Ability to navigate unfamiliar codebases quickly and contribute meaningfully from an early stage.
• Experience with CI/CD workflows and containerization (Docker or similar).
• Willingness to understand the financial data we work with and the formulas you will be responsible for implementing. It is important to be curious and open to learning how financial markets work, as this context is essential to correctly ingest, process, and expose financial data.
• Language Proficiency: Professional proficiency in both English and Spanish to collaborate effectively in our bilingual environment 🗣️.

• Full-time, permanent contract
• Salary range of €35,000–€50,000 gross per year, based on experience
• An office with stunning views of Barcelona
• Flexible working hours and hybrid work options
• Paid day off on your birthday
• Weekly fresh fruit, coffee, and tea
• Friday happy hours (optional)
• Team-building events
• Health insurance and flexible compensation
• Subsidized digital canteen
• Yearly training budget for continuous growth