A guide to hiring a GraphQL developer
GraphQL is a way for apps to ask an API for data. Instead of calling several fixed addresses, the app sends one query that lists the fields it wants, and the server returns exactly that. A GraphQL developer designs the schema that describes your data, writes the code that fetches it and makes sure the API stays fast, safe and easy to change. If your apps make too many calls, or your API is hard to extend, this is the role to consider.
What a GraphQL developer actually owns
The job is wider than adding an endpoint. A GraphQL developer decides how your data is shaped for the apps that use it, and writes the resolvers that fetch each field. They add authentication and permission checks, set limits on expensive queries and watch which fields are slow. They also help front-end teams write queries that are clear and typed. When the schema is planned well, new screens can often be built without any server change at all.
Schema design
The schema is the contract between the server and every app. It lists the types, the fields on each type and how they connect. Good schemas use names that match how the business talks, avoid exposing database tables as they are and mark fields as optional only when they really can be empty. Changes are planned: new fields are added, old ones are marked as deprecated and removed only when no client uses them. This is the skill to test first, because a weak schema is expensive to fix later.
Resolvers and data sources
A resolver is the function that returns the value for one field. It might read from a SQL or NoSQL database, call a REST service or pull from a cache. A strong developer keeps resolvers small, moves business rules into shared code and handles errors in a way the client can show to a user. Your back end developers can work alongside them when the data lives in several systems.
Apollo Server and other servers
Apollo Server is a widely used GraphQL server for Node.js, and GraphQL Yoga is another common choice. Other languages have their own libraries, such as Graphene and Strawberry for Python or gqlgen for Go. Tools such as Hasura can also generate a GraphQL API from a database. The server library matters less than the habits around it, such as clear schema files, tests and a repeatable way to publish changes. If your team writes Node.js, see our Node.js developers or our TypeScript developers.
Federation
When one team owns the whole API, a single schema is enough. As companies grow, several teams may each own part of the data. Federation lets each team run its own GraphQL service while the apps still see one combined graph. Apollo Federation is a well-known way to do this. It brings new work: shared types must stay consistent, and a gateway must route each part of a query to the right service. Federation helps most when team boundaries are the problem, not when a single small team wants to look modern.
Caching and the N+1 problem
The N+1 problem is the most common cause of slow GraphQL APIs. A query asks for a list of items, and then the server runs a separate database call for each item to fetch a related record. A list of many orders can turn into a flood of small queries. The usual fix is batching, for example with DataLoader, which collects the lookups and runs them together. Caching helps too, at the level of a single request, in a shared store or in the client. A developer who can explain this clearly has probably met it in real work.
Auth and query limits
GraphQL gives clients a lot of freedom, so the server must set the boundaries. Permissions should be checked for each field, not only for the whole request. Limits on query depth and cost stop a single request from asking for a huge amount of nested data. Many teams also turn off schema introspection in production or restrict it, and allow only a list of approved queries for public apps. Ask each candidate how they would stop a costly query from slowing the whole system.
GraphQL on the client
The client side matters as much as the server. In React apps, tools such as Apollo Client, urql and Relay send queries, keep a cache of results and update the screen when data changes. A good developer writes queries next to the components that use them, generates types from the schema and handles loading and error states cleanly. If your main need is the app itself, see our React developers, or hire one person for both sides through our full stack developers.
How GraphQL differs from REST
REST gives each resource its own address, and the server decides the shape of the answer. GraphQL has one address, and the client decides the shape. REST is simple to cache and well understood, which makes it a good fit for public and partner APIs. GraphQL suits products where several apps show many related records at once. Neither is always better. Many companies run both, and a developer who knows both can tell you honestly which one fits your case.
When GraphQL makes sense
- Your web and mobile apps need different slices of the same data.
- Screens make many calls to build a single view.
- Several teams build front ends against one set of services.
- You want typed queries and a schema that documents itself.
- Your API changes often, and you want to avoid a new version each time.
If you have one small app and a handful of stable endpoints, REST may serve you well for now. A GraphQL developer will tell you that honestly, and can show you how to move over later, one part at a time.
Reading a GraphQL developer’s background
Ask for an API they built, who used it and what they would change today. Ask how they handled a slow query, and how they planned a breaking change for existing clients. Listen for specific answers about batching, permissions and schema checks. A list of tools tells you little, but a developer who can explain a trade-off, such as when to split a graph, is usually a strong hire.
Interview questions to try
- How would you design the schema for an order, its items and its customer?
- What is the N+1 problem, and how have you fixed it?
- How do you stop a client from sending a very costly query?
- How do you remove a field that some apps still use?
- When would you choose REST for a new API instead of GraphQL?
The best answers give reasons and an example from past work. Be wary of a candidate who treats GraphQL as the answer to every question.
Run a small paid exercise
Give each finalist the same small task based on your real data. It could be a short schema for one feature, a review of a slow resolver or a plan to move one REST endpoint to GraphQL. Pay for the time. Then compare how clear each schema is, how they handled permissions, what questions they asked about your apps and how well they explained their choices.
Agree how the API is kept healthy
Agree where the schema lives, who reviews changes and how a breaking change is announced. Add schema checks to your build, so a change that would break a client is caught before it ships. Keep the repository, the servers and the API keys in your own name, with a separate login for each person. Then nothing is lost if the people change.
Settling in
Give your GraphQL developer access to the code, the data sources and the people who build the apps that call the API. A short walkthrough of your current API and its slowest screens helps more than a long document. A weekly call and one shared board keep progress easy to see. Share the known pain points early, such as a slow list or a hard to change type, because that is where a specialist adds value fastest.
Mistakes to avoid
- Exposing your database tables as the schema, with no thought for the apps.
- Skipping query limits and permission checks on each field.
- Choosing federation before a single schema has become a problem.
- Hiring for the word GraphQL on a resume, and not for how a person designs and tunes an API.
For related work, see our API developers for REST, gateways and webhooks, or our NestJS developers when your server is built on that framework.