Senior Software Engineer

Company: HartleyCo
Apply for the Senior Software Engineer
Location: Greater London
Job Description:

Senior Software Engineer – YC‑Backed Startup

Located in London. This founding team role offers £90 K–£120 K plus equity.

I’m working with an exciting YC‑backed startup in London that’s just closed a multi‑million‑pound funding round and is looking for a Senior Software Engineer to join their founding engineering team.

Despite being early‑stage, they’re already punching well above their weight – with paying customers onboarded and serious traction in their market. This is a rare opportunity to get in at the ground floor of something special.

Responsibilities

  • Working directly alongside the founders to build and scale the product
  • Taking real ownership over technical decisions and architecture
  • Shaping the engineering culture and technical direction from day one
  • Building features that directly impact paying customers

Tech Stack

  • Python
  • TypeScript
  • React/Next.js

Benefits

  • 3 days per week in their London office (hybrid working)
  • Direct impact on product and company direction
  • Work with world‑class founders backed by Y Combinator

Qualifications

  • Strong commercial experience with Python and TypeScript
  • Experience with React/Next.js or similar modern front‑end frameworks
  • Someone who thrives in fast‑paced, early‑stage environments
  • A builder who wants ownership, not just tickets to complete

If you’re a senior engineer looking to step into a founding team role at a startup with genuine momentum, let’s talk.

Location & Employment

  • London, United Kingdom
  • Full‑time, Mid‑Senior level

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Posted: December 23rd, 2025