A guide to hiring a database developer
A database developer designs and builds the way your software stores and finds its data. They plan the tables, write the queries, tune what is slow and make sure a bad day does not turn into lost records. If your app has grown, your reports take forever or nobody is sure the backups work, this is the role to look at. The work sits close to the product, so the person you hire needs to understand how your business uses its data and not only how a database engine works.
What a database developer actually owns
The job goes beyond writing SQL. A database developer decides how information is split into tables and how those tables relate. They write the queries and stored procedures that the rest of the system relies on. They watch how the database behaves under load and fix what is slow. They also own the quiet jobs that save you later, such as migrations, backups and test restores. Good database work feels invisible, because the app simply stays quick and correct.
Schema and data modelling
A schema is the plan for your tables, their columns and the links between them. A good one matches the way your business works. Customers, orders, invoices and products each have a clear home, and a change in one place does not break five others. Developers also decide where to be strict, using keys and constraints that stop bad data at the door, and where to stay flexible. Early design choices are cheap to make and costly to undo, so this is a place to ask for experience.
Query tuning and indexes
A query asks the database for data. An index is like the index at the back of a book: it lets the database find rows without reading everything. The right index can turn a slow page into a quick one. The wrong one wastes space and slows down every write. A developer reads the query plan, finds the step that hurts and decides whether to add an index, rewrite the query or change the table. They test the change before it goes near live data.
Stored procedures, views and triggers
Some logic belongs next to the data. Stored procedures, views and triggers let the database run that logic itself, which can keep rules in one place and cut the back and forth with the app. They also need care. Hidden logic is hard to test and hard to find later. A thoughtful developer uses them where they help, documents them and keeps them in version control like any other code.
Migrations
Sooner or later the design has to change. A column is added, a table is split or the whole system moves from one database engine to another. A migration is the set of steps that does it. Careful developers write migrations in small pieces, try them on a copy and keep a way back. They also plan for the app code that must change at the same time, so the release and the data move together.
Backups and recovery
A backup you have never restored is a hope, not a plan. Your developer should set up regular backups, keep copies in a separate place and test a restore on a schedule. They should also be able to say, in plain words, how much data could be lost and how long a recovery would take. Write those answers down. When something goes wrong, a calm checklist is worth more than a clever fix made in a hurry.
Cloud databases
Many teams now run their data on managed services from the large cloud providers. These take care of servers and some backups, but they do not design your tables or fix your queries. They also add choices about size, replicas and access that affect both cost and safety. A developer with cloud experience will right-size what you pay for, limit who can reach the data and tell you which settings are worth changing.
SQL and NoSQL, and how to choose
Relational databases such as PostgreSQL, MySQL and SQL Server store data in tables and are strong when relations and correctness matter. Document stores such as MongoDB keep whole records and suit data that changes shape. Key-value stores such as Redis hold data in memory and are often used for fast lookups. None of these is better in every case. Ask a candidate how they would choose for your product, and be wary of anyone who always gives the same answer.
How a database developer differs from other roles
A back-end developer writes the services that use the database and often handles simple tables. A SQL developer focuses on queries, reports and stored code. A database administrator runs the servers and the backups. A database developer joins the design and the tuning, and often shares the other jobs on a small team. Choose that depth when the data is central to your product, and the cost of a slow or lost record is high.
The jobs people hire for
One common brief is a fresh data layer for a new product. Another is a rescue, where an existing database is slow, full of duplicate records or hard to change. A third is a move from one engine to another, or from servers you run to a managed cloud service. A fourth is a clean up of reports, so that the numbers on every screen agree. Each brief needs a slightly different mix of skills, so say which one you have.
When a database developer makes sense
- Pages or reports are slow, and the slowness points to the database.
- You are planning a new product and want the data design to be right from the start.
- You need to move to a new engine, a new version or a cloud service.
- Nobody on the team has tested a restore from backup.
- The same figure shows differently in two places, and nobody knows which is right.
If your data is small and your app is simple, a good back-end developer may be enough for now. A database specialist who tells you that up front is on your side.
Reading a database developer’s background
Ask for a problem they fixed and what they measured before and after. Ask what they would do differently now. Look for stories that mention query plans, indexes, migrations and restores, not only a list of engine names. A list of engines tells you little, since anyone can type PostgreSQL on a resume. The better sign is a system that still runs well a year after they left it.
Interview questions to try
- How would you find out why a page that reads from the database has become slow?
- When would you add an index, and when would you leave it out?
- How would you split a large table or change a column without stopping the app?
- How do you prove that a backup can really be restored?
- When would you choose a document database over a relational one?
The best answers give reasons and an example from past work. Be wary of a candidate who names a favourite tool and never explains what problem it solves.
Run a small paid exercise
Give each finalist the same small task based on your real project. It could be reviewing a table design, tuning two slow queries or writing a migration plan for a column change. Pay for the time. Then compare the work, the questions asked and how clearly each person explains their choices. Use a copy of your data with private details removed.
Agree how the work is kept healthy
Agree how schema changes are reviewed, where migration files live and who may change live data. Ask for a short note that explains the main tables and how to add a new one. Keep the database accounts and the cloud account in your own name, with a separate login for each person. Then nothing is lost if the people change.
Settling in
Give your developer read access first, a copy of the data without private details and a list of the pages or reports that hurt most. A weekly call and one shared task board keep progress easy to see. Share the awkward cases early, such as a report that never matches or a table nobody dares to touch, because fixing those is what a database specialist is for.
Mistakes to avoid
- Adding indexes everywhere without measuring what they help.
- Changing live tables before the change has been tried on a copy.
- Keeping backups but never testing a restore.
- Choosing an engine because it is popular and not because it fits the data.
For related skills, see our PostgreSQL developers for one of the most widely used open source engines, or our Python developers for the code that sits on top of your data.