Lead Product Engineer

Societies; City Of London; On-site; GBP 100,000 - 180,000; Full time

Job summary

Societies in London is seeking a Lead Product Engineer to own features end to end—from initial concept to a polished, reliable product used by clients. You will work with our designer and CTO, and collaborate with forward-deployed and research engineers to turn our simulation engine frontier into a product people love.

This senior role asks for strong taste and deep technical skill: focus on latency, UI details, database schemas, API contracts, and scalable architecture.

Qualifications

• 5+ years as software, design, or product engineer with real product shipping.
• Expert in TypeScript; Python is a strong plus.
• Deep systems expertise across browser rendering, API latency, caching, concurrency, and queues.
• Advanced database skills; PostgreSQL migrations and indexing.
• Architectural ownership; define API contracts and service boundaries.
• Experience with AI coding agents (Claude Code, Codex) is a plus.
• Ownership mindset and proactive end-to-end execution.

Responsibilities

• Own features end to end: from design to production and deployment.
• Own the architecture: system design, data models, and API contracts.
• Collaborate with design and CTO to translate vision into implemented features.
• Partner with forward‑deployed and research engineers to scale capabilities.
• Build for performance and reliability for high-stakes decisions.
• Maintain high craft and attention to detail in every ship.

Skills

TypeScript

Python

Systems design

API contracts

Database design

PostgreSQL

Performance optimization

AI coding agents

Ownership

Tools

Claude Code

Codex

Job description

About the role

We're looking for a Lead Product Engineer to own features end to end, from a rough idea to a polished, reliable feature that our clients use every day, and to set the technical bar for how our product gets built. You'll work directly with our designer and our CTO, and partner closely with our forward-deployed and research engineers to turn the frontier of what our simulation engine can do into a product people love.

This is a role for someone with both great taste and deep technical skill. You care about how a feature feels, the latency, the empty states, the small interactions that make a product feel great and you care about the database schema, the API contract, and the architecture that keeps it fast and reliable at scale. You sweat both.

This is a senior role with real ownership. You'll make the architectural decisions that shape the product for years, and as the engineering team grows, you'll set the standard that everyone else builds to: in system design, in code review, in what ships.

What you'll do

• Own features end to end. Scope, design, build, ship, and iterate. From the front-end interaction down through the API to the database, you'll be responsible for the whole vertical slice and the outcome it drives.
• Own the architecture. Make the calls on system design, data models, and API contracts that keep the product fast, reliable, and easy to build on as it grows.
• Work directly with design and the CTO. Translate a design and a product vision into something real, pushing back and contributing ideas of your own. You'll have genuine ownership over what gets built and how it works.
• Partner with FDEs and research engineers. Take the capabilities they built at the frontier of our simulation engine and turn them into reliable, intuitive features that scale to every client.
• Build for performance and reliability. Make features fast, robust, and trustworthy. Our clients make high-stakes decisions on our product; it has to work, every time.
• Raise the bar on craft. Bring taste and attention to detail to everything you ship, and set the standard the rest of engineering builds to.

What we're looking for

• At least 5+ years as a software, design, or product engineer. You've shipped real product to real users, owned features from idea to production, and been the engineer others turn to when the problem is hard.
• Expert in TypeScript, ideally Python too. You write clean, well-structured TypeScript and are comfortable across the stack. Productivity in Python is a strong plus: it's the language of our simulation engine.
• Deep systems expertise. You reason fluently about the whole stack: rendering performance in the browser, API latency budgets, caching, concurrency, and queueing. When something is slow or flaky, you can find out why wherever the problem lives.
• Advanced database skills. You design schemas that last and fix the ones that didn't: indexing strategy, query planning, and zero-downtime migrations, preferably in Postgres.
• Architecture that survives scale. You've designed systems that grew: you've drawn the service boundaries, made the build-vs-buy calls, and defined API contracts that other engineers and systems depend on.
• Great taste. You have strong instincts for what makes a feature feel intuitive, and you sweat the details that turn something functional into something people love to use.
• Fluent with AI coding agents. You're very comfortable working with Claude Code, Codex, or similar harnesses, and you know how to get great work out of them while keeping a high bar on what ships.
• Ownership mentality. You don't wait for a ticket. You see what needs to happen, and you make it happen end to end.

Nice to have

• You've built user-facing production grade AI agents.
• Spent time creating and managing infrastructure.
• You've seen a company go from seed to millions in ARR.
• Experience mentoring engineers or leading a small team.

Logistics

• Location: London, in-office 5 days a week. We build better together, and this role is no exception.
• Salary: £100,000 - £180,000 depending on experience.
• Equity: Up to 0.2%.

Why join now

This is a rare chance to own the product that puts frontier AI in the hands of the world’s most important organisations. You'll work directly with our designer and CTO, ship features that Fortune 500 firms rely on, and own the technical direction of how the product is built. If you want the ownership of an early team, the craft of a product you're proud of, and the technical depth to build it properly, this is the role.