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SDK Engineer - Feature Flags

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Full-time Remote 12d ago

Company:

PostHog empowers developers with tools for product analytics, session replay, and feature flags to enhance product success.

Summary:

The SDK Engineer will focus on developing and enhancing feature flag SDKs used in server-side applications. The candidate should be proficient in languages such as Python, Go, Rust, C#, or TypeScript and experienced with SDK architecture and performance considerations.

Job Description:

SDK Engineer - Feature Flags

Location

Remote (EMEA), Remote (US), Remote (US | EU)

Employment Type

Full time

Location Type

Remote

Department

Product Engineering

Help us to increase the number of successful products in the world!
About PostHog

We’re equipping every developer to build successful products by giving them a suite of products to analyze, test, observe, and deploy new features. We currently offer product and web analytics, session replay, feature flags, experiments, a CDP, SQL access, a data warehouse, and LLM observability… and there’s plenty more to come.

PostHog was created as an open-source project during Y Combinator's W20 cohort. We had the most successful B2B software launch on HackerNews since 2012 with a product that was just 4 weeks old. Since then, more than 100,000 companies have installed the platform. We've had huge success with our paid upgrades, raised bags of money from some of the world's top investors, and have extremely strong product-led growth – 97% driven by word of mouth.

We're growing quickly, but sustainably. We're also default alive, averaging 10% monthly revenue growth and with more than $20m ARR. We're staying focused on building an awesome product for end users, hiring a handful of exceptional team members, and seeing fantastic growth as a result.

What we value

  • We are open source - building a huge community around a free-for-life product is key to PostHog's strategy.

  • We aim to become the most transparent company, ever. In order to enable teams to make great decisions, we share as much information as we can. In our public handbook everyone can read about our roadmap, how we pay (or even let go of) people, what our strategy is, and who we have raised money from. We also have regular team-wide feedback sessions, where we share honest feedback with each other.

  • Working autonomously and maximizing impact - we don’t tell anyone what to do. Everyone chooses what to work on next based on what is going to have the biggest impact on our customers.

Solve big problems - we haven't built our defining feature yet. We are all about acting fast, innovating, and iterating.

Who we’re looking for

We're looking for a pragmatic polyglot engineer passionate about crafting high-quality developer experiences across a range of languages and platforms. You're someone who thrives on improving SDKs that developers enjoy using — ones that are fast, reliable, and feel native no matter the tech stack.

In this role, you'll focus on our feature flag SDKs, used in server-side apps and infrastructure to power flag evaluation. Some of these SDKs make remote requests to our evaluation engine, while others run locally, meaning correctness and performance are equally critical. Many other PostHog products depend on the SDKs, so you'll be working on critical infrastructure that touches many parts of the company.

You should be deeply familiar with at least one of our primary languages/platforms (Python, Go, Rust, C#, or TypeScript), and confident picking up enough of the others to make meaningful contributions across the SDK ecosystem. You’ll work closely with backend, infra, and product teams to ensure our SDKs remain robust and delightful, while also helping us find ways to support more languages more efficiently.

What makes this role unique

  • SDKs are the gateway to everything PostHog – You’ll be shaping the developer experience for every customer using our feature flags product, making your work highly visible and impactful.

  • You’ll work across languages and runtimes – From statically typed servers to dynamic scripting environments, you’ll build idiomatic SDKs that feel like they belong in each language.- You’ll influence local vs. remote flag evaluation strategies – Help us make trade-offs between speed, correctness, and simplicity across a wide array of architectures.

  • You’ll help scale the platform model – One of your major challenges will be finding patterns and tooling to reduce duplication and improve consistency across SDKs, even as we support more platforms.

  • You’ll work on critical paths – Feature flag evaluations often sit in latency-sensitive code paths. You’ll help make sure our SDKs stay fast, observable, and correct.

What you'll be doing

You’ll maintain and extend PostHog’s feature flag SDKs, ensuring they are performant, idiomatic, and correct across a wide range of customer use cases. You’ll contribute to both local evaluation logic and remote integration paths, often working closely with the team that owns our flag evaluation service (written in Rust). You’ll also collaborate with language experts across PostHog to ensure high standards in SDK ergonomics and platform conventions.

A typical week might involve:
- Debugging a subtle evaluation bug in the posthog-go SDK- Prototyping a cross-platform testing framework for SDK correctness- Implementing local evaluation in a new language SDK- Reviewing a community contribution to the posthog-node SDK

Requirements

  • Experience writing idiomatic code in at least one of: Python, Go, Rust, C#, or TypeScript

  • Ability to reason about performance, latency, and correctness in distributed systems-

  • Experience designing and maintaining SDKs or libraries used by other developers

  • Familiarity with API design principles and developer ergonomics

  • Comfortable learning new languages and paradigms quickly

Nice to have

  • Experience with feature flag systems or configuration-as-code tools- Familiarity with local evaluation strategies and the challenges of client/server sync

  • Experience supporting open-source SDKs or working with external contributors

  • Interest in building shared tooling or infrastructure for polyglot SDK development

  • Understanding of observability (logging, tracing, metrics) within SDKs
    We believe people from diverse backgrounds, with different identities and experiences, make our product and our company better. That’s why we dedicated a page in our handbook to     diversity and inclusion. No matter your background, we'd love to hear from you! Alignment with our values is just as important as experience! 🙏


Also, if you have a disability, please let us know if there's any way we can make the interview process better for you - we're happy to accommodate!

Benefits
What we offer in return: