Senior Full-Stack Engineer (Backend-Leaning) | Fully Remote (UK hours) | Full-time

The Sales Centre co; Polska; Hybrid; PLN 180,000 - 300,000; Full time

Job summary

The Sales Centre co is seeking its first software engineer and technical lead to own how the platform is built—from data model to security, payments and background jobs. You will guide the product founder, shape briefs, and manage a two‑week customer migration as you launch the new platform for 60 customers.

You will set up testing, reviews, and production readiness, while mentoring the next engineer and building the foundations for scalable, secure software.

Qualifications

• 5+ years as a professional software engineer, including 2+ years building and running a multi-tenant SaaS product in production.
• Strict TypeScript, React 19 and the Next.js App Router (Server Components, Server Actions, streaming, caching in Next.js 15/16).
• Strong Postgres skills beyond the ORM: schema design, migrations, indexing, query performance and RLS (Supabase a strong plus).
• Stripe in production: subscriptions, webhooks, idempotency, usage or credit-based billing.
• Background jobs and queues (Inngest, Trigger.dev, BullMQ or similar).
• Automated testing as a release gate, CI and Vercel preview deployments.
• Production ownership with Sentry or similar.
• Daily, disciplined use of agentic AI coding tools (Claude Code preferred; Cursor or Codex fine).
• Experience reviewing others’ code as the gate to production and mentoring less experienced builders.

Responsibilities

• Technical direction: architecture, data model, security, testing and code review.
• Approving everything that ships (the product founder signs off on visual changes).
• Setting up the test framework (Vitest, Playwright, GitHub Actions as a merge gate).
• Foundations: Postgres with row-level security, auth, Stripe billing, background jobs, transactional email and third‑party integrations.
• The launch and customer migration, including a two‑week parallel run.
• Production: error tracking, logging, alerts, incident response, performance and cost control.
• Documentation, and helping hire and lead the next engineer.
• Lead the migration and ensure safe go‑live with data integrity.

Skills

TypeScript

React

Next.js App Router

PostgreSQL

Stripe Subscriptions

Background jobs

Automated testing

CI/CD

Code review

Mentoring

Tools

Inngest

Trigger.dev

BullMQ

Vercel

Sentry

Claude Code

Job description

Salary: TBC

About the company

Our client is a UK B2B SaaS platform for property-investment businesses. Its customers source residential properties for investors, negotiate deals and earn a fee, and the platform helps them find opportunities, manage clients and deals, and market themselves. With around 60 paying customers on a white-labelled GoHighLevel setup, the team is now rebuilding the product from scratch as its own platform, with property search, deal management, portfolio tracking, financial calculators, Claude-powered AI features and Stripe billing.

The role

You’ll be the company’s first engineer and technical lead. You’ll own how the platform is built: the data model, security, payments, background jobs, integrations, and what is safe to go live. Your first big milestone is launching the new platform and moving 60 customers off GoHighLevel without losing data.

You’ll work alongside the product founder, who builds every day using Claude Code. Your job is to guide him, not replace him: shape his briefs, catch risks early, and make sure his work and yours don’t collide. A part-time QA analyst tests every release.

What you’ll own

• Technical direction: architecture, data model, security, testing and code review

• Approving everything that ships (the product founder signs off on visual changes)

• Setting up the test framework (Vitest, Playwright, GitHub Actions as a merge gate)

• Foundations: Postgres with row-level security, auth, Stripe billing, background jobs, transactional email and third‑party integrations

• The launch and customer migration, including a two‑week parallel run

• Production: error tracking, logging, alerts, incident response, performance and cost control

• Documentation, and helping hire and lead the next engineer

Your first 90 days

• Weeks 1–2: get set up, learn the code and build plan, and ship a small fix

• Month 1: become the reviewer for everything that ships and take ownership of security and data protection

• Months 2–3: lead the launch and migrate customers across

What you’ll need

• 5+ years as a professional software engineer, including 2+ years building and running a multi‑tenant SaaS product in production

• Strict TypeScript, React 19 and the Next.js App Router (Server Components, Server Actions, streaming, caching in Next.js 15/16)

• Strong Postgres skills beyond the ORM: schema design, migrations, indexing, query performance and RLS (Supabase a strong plus)

• Stripe in production: subscriptions, webhooks, idempotency, usage or credit‑based billing

• Background jobs and queues (Inngest, Trigger.dev, BullMQ or similar)

• Automated testing as a release gate, CI and Vercel preview deployments

• Production ownership with Sentry or similar

• Daily, disciplined use of agentic AI coding tools (Claude Code preferred; Cursor or Codex fine): small PRs, tests before merge, and you read the diff

• Experience reviewing others’ code as the gate to production and mentoring less experienced builders

Nice to have

• Building features on LLM APIs (Anthropic or OpenAI)

• Migrating customers and data between platforms

• Working with large external datasets and third‑party data APIs

• Multi‑tenant security fundamentals (OWASP top 10, secrets, audit logging, UK GDPR)

• GoHighLevel, Resend, MapLibre, SEO and Core Web Vitals

No property knowledge or visual design skills needed. The domain will be taught, and the product founder owns design.

You’ll thrive here if you are

Happy being the only engineer and picking up work without being told. You can explain technical risk in plain English with options and a recommendation, you’ll say when something is a bad idea and then back the decision once it’s made, you ship small and often, and you speak up as soon as something goes wrong.

This probably isn’t for you if

you want a team around you or day‑to‑day management, you’d rather stop a non‑developer from building with AI than help him do it well, you’re mainly a front‑end specialist, or you’d hold up shipping for weeks over architecture debates.