Senior Platform Software Engineer

Location: Remote. Eligible locations in the current Cello job listing: Poland, Estonia, Germany, Portugal, Spain and the United Kingdom, within CET +/-3 hours. Cello is based in Munich, Germany. This role is remote across the eligible locations above; Munich office attendance is not required. Salary is not published.

Why join

• AI-powered infrastructure company with $10.3M in funding from top-tier investors.
• Exciting product: APIs, attribution models, MCP integration, AI-based recommendation engines, and assistants - not your typical CRUD app.
• Real traction: 30+ new customers every month , 10M+ end users monthly .
• Small team, so you'll genuinely shape how we build things.
• You'll touch everything from frontend widgets to backend infrastructure to data pipelines. The work doesn't get repetitive.
• We actively learn about new tech and AI tools and adopt where we can , we have to, because our customers do.
• Remote-first, but we get together regularly - company-wide and as an engineering team.
• The founding team consists of serial founders and experienced big-tech operators from Twilio, Wise, and Skype .

What We’re Building

We help SaaS companies turn their users and partners into a sales channel through referrals, sharing, and recommendations - 10M+ end users interact with our system every month.

Our widgets live inside customer products, which means your code runs in environments you don't control . On top of that: APIs that customer developers integrate against, and a portal where customers manage their campaigns and analytics.

Under the hood: attribution across complex user journeys, AI-based recommendation engines, multi-tenant infrastructure serving hundreds of customers, scaling millions of events. Deeper than you'd expect from a referral tool.

Our product is integrated by customer developers - and that world is changing fast. The people building against our APIs and widgets range from corporate engineering teams to solo founders using AI coding agents . Keeping up with how developers work today, and making sure our product fits into all of those workflows, is one of the more interesting challenges here.

Your Mission

• Stack : AWS · Terraform · NestJS · PostgreSQL · GitLab CI/CD
• You work directly with stakeholders - no walls, no ticket factory.
• Manage AWS infrastructure - architecture, reliability, security, and cost. No infrastructure team above you.
• Design and maintain CI/CD pipelines that let engineers ship confidently and fast - from commit to production with zero manual steps.
• Sometimes we ship fast to learn, sometimes we slow down to fix the foundation - you'll help decide where to lean.
• Real influence on architecture and product direction, not just coding tickets.
• Help us adopt the latest AI improvements to speed up how we build and ship.

About You

Required

• Good communication skills and a collaborative attitude
• Experience building systems at real scale: high traffic, large user base, high availability
• Deep AWS expertise across compute, messaging, storage, networking, and observability - not just familiarity, but operational instinct built from running things in production
• Strong experience with Infrastructure as Code (Terraform or similar) - you version everything, you don't click around in consoles
• Solid distributed systems thinking: ordering guarantees, idempotency, retries, at-least-once delivery, partial failure recovery
• Experience running PostgreSQL in production - configuration, connection pooling, migrations, performance, backup and restore
• Enough application-layer literacy to read TypeScript/Node.js (NestJS) code and understand what a service is doing, not just that it's running
• You know when "good enough" is right - and when to invest in quality
• You are a strong problem solver - you can break down complex, ambiguous problems and ship pragmatic solutions, not just debug what's already in front of you
• You contribute ideas and challenge assumptions, not just execute
• You're genuinely curious about the product itself - you want to understand what we're building and why, not just pick up tickets and ship code.
• You live at the bleeding edge of agentic coding. Claude Code, Cursor, multi-agent setups, MCP servers, whatever ships next, you're using it and pushing it to its limits. We move fast on adopting what works
• That said, you know how code and systems actually work. You can debug, reason about architecture, and carry your weight in a codebase without an AI assistant holding your hand.
• Strong work ethic - you take ownership, ship what you commit to, and don't need to be chased

Nice-to-haves

• Strong opinions about observability , structured logging, distributed tracing (OpenTelemetry), dashboards and alerting built for on-call humans, not vanity metrics
• Experience operating event-driven architectures under load (SQS, Kafka, or similar) , you know what failure looks like before it becomes an incident
• Familiarity with data warehousing / analytics (e.g. ClickHouse, Snowflake, or similar)