Backend Engineer - Billing Systems

Who we’re looking for

Someone has to make sure PostHog actually gets paid. That's us.

We have 14+ usage-based products, subscription add-ons, and soon seat-based pricing with credit pools. Every dollar PostHog makes flows through what we build. If we screw up, customers lose trust and churn - doesn't matter how good the product is. Execs, product, and GTM teams can't make good decisions without the data we provide.

We launch new products all the time and we always want to do what makes sense for customers rather than fit things into a rigid existing system. That means we need to build billing infrastructure that's modular enough to support whatever we throw at it next, fast enough to iterate on without breaking things, and reliable enough that the numbers are always right. Getting all three perfect at once is impossible - finding the right balance is the main challenge. Are we there yet? Not even close. But you'll help us get there faster.

What you'll be doing

• Scaling our billing system to $100M+ revenue by the end of 2026, and well beyond.
• Building billing primitives flexible enough that launching a new pricing model doesn't require rearchitecting everything.
• Making our usage reporting and limiting near-realtime.
• Turning usage and messy raw invoice data into actionable internal reports, accurate forecasts, and compliant financials.
• Making all of the above go brrr.

Example projects:

• Implementing a new, ledger-based revenue model and re-building all dashboards and investor reports on top of it.
• Making billing the source of truth for pricing, subscriptions and invoicing.
• Shipping 5+ pricing launches and changes this quarter, including two new pricing models.

You’ll fit right in if:

• Strong backend engineer. Python, SQL, and complex data modeling should feel like home.
• Edge cases make you excited, not anxious.
• Experience with data pipelines, task queues, and workflow orchestration - we still have a lot of Celery but are leaning more into Temporal and Dagster.
• If you've done something manually twice (or seen someone else do it) - you're already building an automation or an internal tool to make it easier.
• Happy paths are maybe 10% of billing. You treat error handling, rollbacks, and retries as the actual work - not TODOs you'll "get to later".
• You don't need someone to tell you what to build. You've started a company, led a major project from scratch, or shipped an impressive side project.

Nice to haves:

• You've built and scaled usage-based billing systems before (and have the scars to prove it).
• You get weirdly excited about revenue modeling, forecasting and accounting ledgers.
• You have a decent guess which one of these we made up: Q2C / AR / B2R / GAAP / ASC 606 / NRR.

This role is not for you if:

• You only want to work with other engineers - billing touches every team at PostHog, from product to finance to GTM to marketing.
• You need clearly defined requirements before you start building.
• You think billing is a solved problem - we thought so too, once.