What is a full-stack developer, and is one enough for your project?

The managing director of a 25-person wholesaler has had enough of orders being typed in three times: in email, in a spreadsheet and in e-conomic. She posts a job for a full-stack developer and gets 40 applications. Half of them list more than 20 technologies each, and she has no idea how to choose. It is a very common situation, and it comes from the fact that the title full stack means slightly different things from person to person. Let us make it concrete.

What is a full-stack developer?

The stack is the layers a digital product is made of. At the top is the user interface in the browser or app. Below it sits the server with the business logic, then the database, and at the bottom the infrastructure it all runs on. A full-stack developer can work in every layer and understands how they connect. That rarely means the person is an expert in all of it. Most are strongest in one or two layers and competent in the rest.

We explain the difference between the two halves, frontend and backend, with a webshop example in frontend vs backend. If you are unsure where design fits in, read web designer vs web developer.

What does a full-stack developer do in a typical week?

To make the role tangible, here is a realistic week for a full-stack developer building the wholesaler’s order system:

• Monday: reviews the week’s tasks with the managing director and clarifies how credit customers should be handled.
• Tuesday: extends the database with customer-specific prices and writes the migration.
• Wednesday: builds the API that fetches prices, and the screen where sales staff create orders.
• Thursday: connects orders to e-conomic so the invoice is created automatically, and tests what happens on errors.
• Friday: fixes two bugs from last week’s release, deploys the new version and checks logs and backups.

Notice that one feature, customer-specific prices, touches every layer within a week. That is exactly the strength of a full-stack developer: a whole feature can be built by one person with no waiting on others.

When is one full-stack developer enough?

What we see most often is that one developer is exactly right for building the first version, and the problem arises afterwards. The product becomes business-critical, and all the knowledge sits in one head. When that person changes jobs, the company is left with a codebase nobody else knows. Plan from the start who should be able to take over, and make sure the code lives in your own repository. Our guide on who owns the code covers what you need in place.

What does a full-stack developer cost in Denmark?

A worked example: the wholesaler’s order system with login, customer pricing, order entry and an e-conomic integration is estimated at 200 hours. With a freelancer that comes to DKK 160,000–280,000 depending on the rate. On top comes maintenance, which under the 15–20 % per year rule of thumb means DKK 24,000–56,000 a year. Alternatively, the same job can be priced as a fixed project where the supplier carries the risk of overruns. We have collected market rates in developer hourly rates in Denmark.

What are the risks of relying on one developer?

• All knowledge sits with one person, and holidays or illness stop development.
• Nobody reviews the code, so bugs and security holes are found late.
• The developer picks a niche technology that is hard to find others for.
• The code sits on the developer’s own account, and access is personal.
• There is no documentation, because it is all in one person’s head.
• The design becomes the developer’s best guess, because no UX skills are involved.

All of these risks can be handled with a few agreements from the start: code in your own repository, a widely used stack, brief documentation of architecture and deployment, and a second developer who reviews the code now and then.

Which myths exist about full-stack developers?

• Myth: a full-stack developer can do everything. In reality most are strongest in one or two layers, which is fine as long as you know which.
• Myth: full stack is a junior role. Many of the most experienced developers work across the stack precisely because they have seen every layer fail.
• Myth: one full-stack developer replaces a design team. Interfaces that customers must use without help benefit from a UX designer, even when the developer has good taste.
• Myth: the more technologies on the CV, the better. Depth in a widely used stack is worth more than a passing acquaintance with twenty.
• Myth: a full-stack developer handles operations automatically. Monitoring, backups and security updates need to be agreed and prioritised, or new features push them aside.

The last myth is the one that costs the most. We regularly take over products where the developer built solid features, yet nobody had tested whether the backup could actually be restored. Always ask who owns operations, and what happens on a Saturday evening if the product goes down.

How to assess a full-stack developer

For the interview you can use these questions. They do not require you to be technical, because you are listening for whether the answers are concrete:

1. Tell us about a product you built from scratch and still maintain.
2. How do you make sure an integration error does not stop the whole system?
3. How do you deploy a new version, and how do you roll back if something goes wrong?
4. How do you protect personal data in a product like ours?
5. What would you do so another developer can take over your code?
6. Which part of the stack are you strongest in, and where do you need help?

The last question may be the most important. A developer who can honestly say where their skills end is far easier to work with than one who claims to do everything. You will find more advice in how to hire a web developer.

Full-stack freelancer, agency or employee: what suits you?

If you have ongoing development for at least one full-time role all year, and want to build knowledge in-house, an employed full-stack developer is often the right long-term choice. If you have a defined project or fluctuating needs, a freelancer or an agency is cheaper and more flexible. We go through the numbers in hire a developer or use an agency.

At Ceptiv we work as one senior team in TypeScript throughout: React and Next.js on the web, React Native for apps and the same language on the server. That gives you the benefits of full stack, where one feature is built from screen to database without hand-offs, while the knowledge is shared across more than one person. You own the code and data, and we give a fixed price before we start. If you are building a first version, see MVP development, or describe the job and get a proposal within 24 hours.