Do I need a database for my app? A plain answer

Maybe Claude Code mentioned a database, or your app forgets everything when you refresh the page. Either way, you're asking a fair question: do I need a database for my app? This page gives you a quick test, which kind to pick, what to ask Claude Code, and what changes once your app is online. I build fline, hosting for apps people build with Claude Code on their own computer, so the last part says what fline does when your app needs one.

When does an app need a database?

An app needs a database when it has to remember something between visits. The pages show things. The database is the part that keeps them after someone closes the page.

Answer these four questions about your app:

1. Does anyone sign in?
2. Does anyone save something, like a booking, an order, a message or a form?
3. Does it need to still be there tomorrow?
4. Does one person see what another person saved?

If you answered yes to any of them, your app needs somewhere to keep that information, and that's usually a database. If you answered no to all four, as you might for a menu, a portfolio or a page about your bakery, you can leave it out.

A common sign that you already need one: you add something, refresh the page, and it's gone.

What database should I use for my app?

For most small web apps, one ordinary database is enough. A common choice is Postgres, a general-purpose database that keeps sign-ups, bookings, orders and messages in tables your app can search.

You may also hear about a cache, such as Redis or Valkey. A cache keeps things your app needs often close at hand, so it can answer faster. Most small apps start without one, and it's usually not where your important records live.

You don't have to choose on your own. If you build with AI, including what people call vibe coding, ask the tool that wrote your app. Claude Code can read your project and tell you which kind of database it expects. Add more only when Claude Code gives you a reason you understand.

What to ask Claude Code first

Ask Claude Code two things before you put your app online: what your app needs to remember, and where it keeps it today.

Does this app need a database? Tell me in plain words what it would keep, and where it keeps things now.

Some apps keep their data in a single file inside the project folder, or in a database that runs only on your computer. That works while you're the only one using it. The next question tells you whether it will keep working for other people.

Once this app is online, will what people save still be there after a restart or an update? If not, what does it need?

If Claude Code says your app needs a database, that's normal.

What changes once your app is online

Your app online needs a database that's online too. A database on your computer stays on your computer, and your app online can't count on reaching it. So the database has to live somewhere your app can reach, with an address and a password of its own.

That's the part a host can take off your hands: running the database, keeping it reachable, and giving your app its address. If your app still only opens on your computer, start with why your app only works on your computer, then how to get your Claude Code app online.

Two things are worth knowing before you trust any host with records you can't lose:

• The address line holds a password. Treat it like any other key. Don't paste it into the chat with Claude Code. Is it safe to give Claude Code your API keys? explains where keys should go instead.
• What happens if data is lost. Ask whether the host keeps copies you can restore, and keep your own copy of anything that matters.

Where fline fits

When your app needs a database, Claude Code can have fline create one, and fline runs it for you.

• What you get. fline can create the database your app needs: Postgres, or a fast cache with Valkey, which works like Redis.
• How your app finds it. Your app needs the database's address, one line that also holds its password. If that line needs you, Claude Code asks you to copy it from your fline dashboard and tells you where it goes.
• It belongs to your account, not to one project, so more than one of your projects can use it. You can see it on the Services page of your fline dashboard.
• Locked with a password and encryption. It's on the internet so your app can reach it, it takes only encrypted connections with its password, and you can limit it to addresses you list.
• Pause it or delete it. You can pause a database and resume it later. If you delete one, its data is kept for seven days, then destroyed.

My app needs a database. Have fline create one for it.

What it doesn't do yet: each database comes in one small size, with 1 GB of memory and room for about 8 GB of data. We don't promise backups yet, there's no way to restore, and there's no button to download your database, so keep your own copy of anything you can't lose. During the private beta everything runs on one rented machine, so fline suits trying your app with your first users. A database of your own has the details, and what fline does today lists the limits, with the date they were checked.

fline is free during the private beta, with no card, and we open accounts by hand, a few at a time. Ask for early access.

Questions people ask

What database should I use for an app I built with Claude Code?

Ask Claude Code first, because it can read your project and tell you which kind of database your app was written for. For most small web apps that's one ordinary database, and Postgres is a common choice. A fast cache such as Valkey is an extra that some apps use to answer faster. Start with what your app needs.

Do I need a database for a simple website?

Not if it only shows information, like a menu, your opening hours or a portfolio. You need one when visitors leave something behind that you or they will want later, such as a booking, an order, a message or an account they sign in to. A quick test is to save something, refresh the page and see whether it's still there. If it disappears, your site needs somewhere to keep it.

Why did my free database get paused?

Some free plans pause a database that sees little use for a while, to save resources. If that's what happened, the service that runs it says how to resume it, often from its own dashboard. On fline, you can pause a database yourself, or ask Claude Code to, and resume it later.

Can fline bring back my data if something goes wrong?

Not yet. fline doesn't promise backups, there's no way to restore, and there's no button to download your database, so keep your own copy of anything you can't lose. Putting an earlier version of your app back doesn't change what's in your database. If you delete a database, its data is kept for seven days and then destroyed. Claude Code should ask you before it deletes one.

Is my database on the internet?

On fline, yes, so your app can reach it. It takes only encrypted connections, and only with its password. You can also limit who can reach it: open the database on the Services page of your fline dashboard and add the addresses you want to allow under "Who may reach it".

Can I use a database I already have?

Yes. If you already run a Postgres, MySQL, MongoDB, Redis or RabbitMQ service, your app on fline can use it instead of a new one. Claude Code tells fline what kind it is, and you type its address on fline's private page, the same page you use for keys, rather than in the chat.