What is the difference between hashing, encryption and encoding? Give a backend use for each.

Encoding changes the format, encryption hides data behind a key, and hashing is one-way.

Encoding changes how data is represented, for transport or storage. Examples are base64, URL encoding and UTF-8. It uses no key, and anyone can reverse it. So it gives no security. For example, a JWT payload is base64url-encoded, and anyone can read it.

Encryption transforms data with a key. Only people with the key can reverse it. Use it when you need the original data back. Examples are third-party API credentials, or sensitive fields like national ids. Use AES-256-GCM or a KMS (Key Management Service, a cloud service that stores and uses keys for you).

Hashing is one-way. It turns any input into a fixed-size value called a digest, and you can't reverse it. Use it for integrity checks. Also use it for passwords, with slow, salted algorithms like Argon2id. A salt is a random value added to each password before hashing. For passwords, you only ever check them. You never need the original back.

The classic trap: passwords are hashed, not encrypted.