What Is File Storage?

Profile pictures, PDFs, videos, product photos. Sooner or later your app has to hang on to files that people upload, and they have to live SOMEWHERE. I built a lil Bulk Image Processor that chews through 100 images in about 5 minutes... and every one of those images needs a home when it's done. This lesson covers where files should live, why, and what to look for in a file storage service.

Files Are Different From Data#

A database is great at small, tidy pieces of information. A name, an email address, an order total. It was never built to hold a 20 MB video.

So you might think, fine, I'll just save uploads to my server's disk. That falls apart fast too.

• Many hosts wipe the disk when your app restarts or redeploys, so uploads vanish.
• Apps often run on more than one server, and a file saved on one isn't on the others.
• Serving big files is slow and it eats your server's bandwidth.

So apps split the job. Files go to a storage service, and the database keeps a small record that points to each file.

What Is Object Storage?#

Most file storage services use a model called object storage. Three words and you've got it.

• Bucket. A container for your files, kinda like a top-level folder. You might have one for user avatars and another for documents.
• Object. A single file, plus a lil info about it, such as its type.
• Key. The object's name inside the bucket, like avatars/user-123.png. It looks like a folder path, but it's honestly just a name.

You put objects in with an API call and get them back by key, or through a URL.

Where File Storage Sits in Your App#

Step 1. The User Picks a File#

They choose a photo on your upload page.

Step 2. Your App Sends It to Storage#

Either your server uploads it, or your server hands the browser a short-lived link so it can upload straight to storage.

Step 3. Storage Saves It#

The file lands in your bucket under a key.

Step 4. Your Database Remembers Where It Is#

You save the key or URL right next to the user's record.

Step 5. Your Pages Show It#

When the page loads, it uses that URL to display the image.

  Browser --- upload ---> File storage (bucket)
     |                          |
     v                          v
  Your app --- saves key ---> Database
     |
  Page shows the image using the stored URL

Public and Private Files#

Not every file should be visible to the whole world. A product photo can be public. An invoice or somebody's ID document absolutely can't.

Storage services let you keep a bucket private and hand out temporary links when someone's allowed to see a file. You'll set that up in the R2 chapter.

What to Look For#

When you're comparing file storage services, ask yourself these questions.

• Is it S3 compatible? Amazon S3 set the standard. Lots of services speak the same API, so the same code and tools work with them.
• What does storage cost? It's usually priced per GB stored per month.
• What does downloading cost? Some services charge every time a file gets served, which is called egress. For busy apps that can be the BIGGEST part of the bill.
• How do public and private files work? Look for easy temporary links.
• Is it fast for your users? A service with a global network serves files from somewhere nearby.

The Service in This Module#

This module covers Cloudflare R2, an object storage service that works with the S3 API. Its chapter walks through how R2 works, how to set up and lock down a bucket, and then how to upload files from code.

TL;DR#

• Files don't belong in your database or on your server's disk
• Object storage keeps files as objects, inside buckets, named by keys
• Put the file in storage and its key or URL in your database
• Keep files private by default and use temporary links when you need them
• Compare services on S3 compatibility, storage cost, download cost and speed
• This module covers Cloudflare R2

What's Next?#

Next up is the Cloudflare R2 chapter, where you'll see object storage doing its thing for real...