"Full stack engineer" is the most useful and least precise title in software. In one company it means someone who builds a React front end and a Node back end. In another it means a backend engineer who can fix a CSS bug. In a third it means the founder's first hire, who has to do everything.

The CIPD guidance on selection methods explains interviews and skill-based assessments. Use a consistent, job-relevant assessment rather than judging candidates on presentation or familiarity alone.

That ambiguity is why full stack developer recruitment for SaaS startups goes wrong so often. This guide sets out how to decide what you need, where to find it, and how to test for it.

Start by defining your stack, not the title

Before you write the advert, write down the stack you actually have and the work this person will do in the first six months. A useful template:

Question Your answer
Front end framework and language e.g. React with TypeScript
Back end language and framework e.g. Node, Python or Go
Database and infrastructure e.g. Postgres on AWS
Main work in six months New features, performance, integrations, billing
Share of front end vs back end e.g. 60/40
Who they work with Product, design, other engineers, customers

That table tells a candidate more than "full stack engineer, 3 to 5 years' experience".

Which kind of full stack engineer do you need?

  • The generalist builder. Ships end to end, copes with ambiguity, owns features from idea to production. Ideal for seed and Series A companies.
  • The product engineer. Strong on user experience and product thinking, builds the thing customers actually see. Good where speed of iteration matters.
  • The backend-leaning full stack. Spends most of the time on APIs, data and integrations, with the ability to ship the interface. Good for B2B SaaS with heavy integration work.
  • The frontend-leaning full stack. Deep on interface quality, with working back-end ability. Good for consumer-style products.

Trying to hire all four profiles in one person can make the brief unrealistic. Decide which capability matters most for the next six months.

Where good full stack engineers come from

The market for engineers is crowded with candidates and short of people who are actually good, and the best are rarely actively applying. Useful sources include:

  • Engineers at companies one or two stages ahead of you
  • Open source contributors on projects you use
  • Engineers who have recently left a startup that raised, struggled or shut down
  • Referrals from your existing engineers, which are usually your best signal
  • Direct outreach with a specific, honest message about the problem you are solving

Generic outreach ("exciting opportunity at a fast-growing startup") is invisible. A message that names the product, the stack and one real problem gets answered.

How to test for the job

Avoid long take-home tasks and abstract algorithm quizzes. Test what the job needs.

  • A short practical exercise (60 to 90 minutes). Build or extend a small feature in your stack, in pairing or live.
  • A code review discussion. Give them a piece of code with problems and ask what they would change.
  • A system design conversation. Appropriate to their level, based on a real problem from your product.
  • A collaboration check. Meet the product manager or designer they would work with.

Watch for judgment as much as output: how they handle trade-offs, what they ask before building and how they react to feedback.

Compensation and equity

Engineering compensation moves quickly and varies by location, stage and remote policy, so check current benchmarks rather than relying on last year's number. At startups, equity is part of the offer, and good candidates ask about the percentage, the strike price, the vesting schedule and the last funding round. Have answers ready.

Hiring in a competitive market

  • Be fast. Strong engineers are usually interviewing at several places. Aim to complete the process within three weeks.
  • Be specific. Show them the real codebase, the product roadmap and who they will work with.
  • Be honest about the mess. Candidates respect a founder who says "the billing code is a disaster and we need help" far more than a pitch of perfection.
  • Make the engineering leader visible. People join people.

Common mistakes

  • Hiring for a stack in fashion. Hire for fundamentals and learning speed, not for the latest framework.
  • Ignoring the product instinct. In a startup, engineers who understand the customer ship better work.
  • Skipping references. A call with a former colleague tells you more than a fourth interview.
  • Hiring a senior to do junior work. They leave.
  • Hiring a junior without mentorship. Same result, slower.

Hiring engineering talent alongside customer-facing teams

At Wundertalent we place engineers alongside our core Solutions and Implementation work, because SaaS companies that hire well in both camps ship and deliver faster. We recruit full stack, AI, backend and frontend engineers for SaaS and AI companies in the UK, and full stack and React engineers in the US. If you already work with us on Solutions hires, see our Solutions & Implementation page; for engineering, book a call.

Related hiring guides

Explore our Solutions & Implementation recruitment service or contact Wundertalent to discuss your hiring needs.