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Database Schema
Database Schema The tables for the reels app: users, posts and likes. Store only the S3 key , like videos/2026/09/abc.mp4 , in the database. Make a fresh presigned link each time a page loads. Saving the full presigned URL in the database. After about 20 minutes every video says Access Denied .
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What this card says
What it is
The tables for the reels app: users, posts and likes.
Key design point
Store only the S3 key, like videos/2026/09/abc.mp4, in the database.
Make a fresh presigned link each time a page loads.
Common mistake
Saving the full presigned URL in the database. After about 20 minutes every video says Access Denied.
| Design choice | Reason |
|---|---|
| Video file in S3, only s3_key in MySQL | Databases are bad at storing large files; S3 is cheap and… |
| password_hash column, VARCHAR(255) | Stores bcrypt/argon2 hashes, never plain passwords |
| likes composite primary key (user_id, post_id) | The database itself prevents double likes |
| ON DELETE CASCADE | Deleting a user removes their posts and likes – no orphan… |
| CHECK on post_type | A video post without a key, or a text post without text, is… |
Learn more in the lesson: 16.4 Database Schema