Software Engineer - Backend

About the Position

Software Engineer - Backend

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About Cala

AI is about to do a real share of the world's work. Whether we can trust it comes down to one thing: what it knows.

Cala is building the knowledge layer for that future. We're turning everything publicly known about the world (every company, person, filing and regulation, and every connection between them) into a single graph of verified facts that any agent can query. What Bloomberg and LexisNexis became for human professionals, Cala is becoming for AI: built with agents, for agents, at a scale no team of people could ever reach.

We raised a €7M pre-seed led by Lightspeed, launched in June, and global enterprises already run on Cala in production. We're based in Barcelona and San Francisco, and still small enough that everyone who joins now helps define what Cala becomes.

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About the Role 💡

We're looking for an experienced backend engineer with depth.

You'll come from a Backend Engineering background – Python, APIs, distributed systems – but what matters most is your motivation to build across layers and solve complex problems end-to-end. Backend is your anchor, but this is a high-impact engineering position for someone who enjoys working with multiple parts of the system rather than in a narrow specialization.

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Responsibilities 🛠️

• Design and build backend services using Python (FastAPI)
• Architect data storage and retrieval systems using SQL and NoSQL technologies (Postgres, Redis, Cassandra, graph databases)
• Develop and maintain scalable pipelines (batch and streaming)
• Work with cloud infrastructure on AWS and containerized environments (Kubernetes)
• Experiment with emerging AI engineering tooling (coding agents, MCP ecosystems, etc.)
• Collaborate on system design and cross-functional architectural decisions
• Contribute to a culture of clean, pragmatic, high-quality engineering

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Requirements 🔎

Strong background in:

• Backend Engineering (Python, APIs, distributed systems)

Technical stack we commonly work with:

• Python
• FastAPI or similar frameworks
• AWS
• Kubernetes
• SQL and NoSQL databases (Postgres, Redis; Cassandra or graph databases are a plus)
• Search systems or information retrieval is a nice to have
• DevOps practices

Profile:

• 4+ years of hands-on backend engineering experience, with real depth – you've gone deep, not wide and shallow
• Able to reason about and justify your technical decisions: pros, cons, why A over B
• Builders at heart: hackathons, side projects, open-source contributions, active GitHub are all highly appreciated
• Curious about how things work end-to-end, including the parts adjacent to your own – infrastructure, data, the systems your code runs on
• Curious about the AI ecosystem and modern developer tooling
• Comfortable in a fast-moving startup environment
• C1+ level in either English or Spanish (fluency in either is acceptable)

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Why Cala? ✨

• Work alongside founders with a proven track record in AI and startups
• Build foundational AI systems with an "AI for good" focus
• High ownership, high autonomy, real technical challenges
• Join at an early stage and help shape both technology and culture
• A supportive, inclusive, and horizontal team environment

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Locations:

• Barcelona, Spain
• San Francisco, United States

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Apply

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