Full-Stack Engineer
What the work looks like, the stacks behind the title, what each level means and the training that helps, then how interviews run and how to prepare for each step.
What a full-stack engineer actually does
The whole path of a feature, from the screen users see to the data behind it, owned by one engineer.
A full-stack engineer builds features end to end: the interface, the API behind it and the data model underneath. The code matters, and so do the choices around it: where the logic should live, how the front and the back agree on data, and how to ship a feature quickly without leaving problems for later.
Most full-stack engineers have a stronger side, often the backend or the frontend, and enough depth on the other to deliver a feature alone. They work closely with product and design, and often look after the deployment and monitoring of what they ship.
More and more teams also work with AI coding tools such as Claude Code, Cursor or GitHub Copilot, and expect engineers to use them with judgment.
- Building a feature end to end, from the database to the screen
- A product discussion on the scope of a new feature
- Reviewing the code of other engineers on both sides of the stack
- Shipping behind a feature flag and watching how it behaves in production
- Time on tests, performance and technical debt
Many companies, from large tech groups to startups, hire their full‑stack engineers under the title Software Engineer, sometimes followed by Full‑Stack in brackets.
Behind the broader title, the stack and the product described in the job ad show where the work really sits: true full‑stack work, or a role closer to the backend or the frontend. On your CV and in interviews, describing the features you shipped end to end tells a company more than the title alone.
The same title, very different stacks
Most full-stack searches are defined first by the pair of technologies the team uses on each side, then by the ground every full-stack engineer shares.
What each level means in practice
Titles vary from one company to the next. What changes from one level to the next is the scope you own and the decisions you take.
- Builds small features on both sides with code review
- Learns the codebase, the tests and the tools
- Fixes bugs with support from the team
- Owns features from the database to the screen
- Designs simple APIs and the screens that use them
- Ships, monitors and fixes what they build
- Designs features and data models for the team
- Leads technical decisions and their trade‑offs
- Mentors other engineers on both sides of the stack
- Sets technical direction across several teams
- Owns architecture choices between front and back
- Writes the design documents others build on
The paths into the role, and what really counts
Companies look first at the features you have built and shipped. Education and certifications help most early in a career, or to change field.
- Engineering school or master's in computer scienceThe most common path in France, and often expected by large companies.
- University degree in computer scienceThe most common path in the US, at bachelor's or master's level.
- Bootcamp or self-taught, with real projectsCommon in full-stack, since most bootcamps teach a complete web stack through real projects.
- Moving from a nearby roleFrontend or backend engineers often widen their scope to the other side of the stack.
Our view: in full-stack, a feature you shipped end to end and can walk through often says more than any certificate.
A conversation with a senior tech recruiter
Your first interview is with one of our senior tech recruiters, who knows the role, the stacks and the levels in this guide. The conversation covers your own work through real examples, and the technical exercises come later, with the company. Before the call, we send you the six themes we will cover so you can prepare your examples.
- What you owned yourselfThe features you built end to end, the parts you owned on each side and your own part in the team's work.
- Your environment and its constraintsNumber of users, team size, legacy code, deadlines or a small team where everyone wears many hats: what shaped your technical choices.
- The decisions you madeWhere to put the logic, which framework or data model to use, the options you compared and the reasons for the one you kept.
- The impact of your workWhat changed thanks to your work, with numbers when you have them: usage, conversion, speed of delivery or incidents.
- How you work with other teamsYour work with product, design and the other engineers, and how you settle a disagreement.
- What you want nextThe kind of product, team and scope you are looking for in your next role.
- Features shipped end to end
- Real depth on one side
- Product sense
- Speed with quality
The same ground for every candidate. For a given role, every candidate answers the same final questions, built with the hiring manager around what the role really needs.
Ready for the next steps. After our call, we tell you how the company runs its interviews, who you will meet at each step and what each step is meant to assess.
What the company will assess, step by step
Each company runs its own process, and we walk you through its steps before you start. Full-stack processes often combine the steps below, and the depth expected at each step grows with your level.
- A coding exerciseLive coding or a take-home on a realistic problem, often a small feature with an API, a database and a screen.
- System designDesigning a product feature from a short brief: the data model, the API, the interface and how it scales.
- A deep dive on your past workOne feature or product you built, discussed in depth: your choices on each side, what broke and what you would change today.
- Meeting the manager and the teamHow you work, how you take decisions with others and what the team expects in your first months.
- ConfirmedYou deliver a working feature on both sides, explain each choice you make and follow the interviewer on the harder parts of the design.
- SeniorYou lead the discussion, go deep on your stronger side and on two or three key choices, and point out the limits of your own solution before you are asked.
- Staff and PrincipalYou run most of the interview as a peer, weigh the long-term consequences of each choice and connect the feature to the product and the other teams.
How to prepare as a full-stack engineer
Practical advice for each step of a full-stack process, from the way you introduce yourself to the questions you ask at the end of each interview.
Start with the features and products you built, their users and your part on each side. Mention your stack in one sentence, then close with what you want next.
For each one, prepare the context, the constraints, your decision, the options you set aside, the result and what you would change today. Say "we" for the team and "I" for your own part.
Interviewers often ask where your real depth lies. Say it clearly, give an example, and show how you work on the other side when a feature needs it.
In system design, ask about the users, the main flows and what matters most before you draw anything. Then explain each choice with its trade‑off, from the database to the screen.
Keep to the time suggested and add a short README with your choices, their trade‑offs and what you would add with more time. A clean API, tests and a usable screen count as much as the result.
Rules on AI coding assistants differ from one company to the next, and sometimes from one step to the next. Ask before each step, and when they are allowed, explain what you ask the tool and how you check its output.
- Walk us through a feature you built end to end: the data model, the API and the interface.
- Where would you put this logic, in the frontend or in the backend, and why?
- Tell us about a bug or an incident in production, and what changed afterwards.
- How do you test and deploy your code?
- How is the work split between frontend, backend and full-stack engineers?
- Who decides the scope of a feature, and how?
- How often do you deploy to production, and how?
- Who is on call for the features I would build?
- How much time goes to technical debt?
- How does the team use AI coding tools day to day?
Where full-stack engineers come from, and where they go
The roles people most often hold before this one, and the ones they most often move to.
Some full-stack engineers also become tech leads or founding engineers in startups.