Session storage pattern in Redis - Step-by-Step Execution

Concept Flow - Session storage pattern

User logs in

↓

Generate session ID

↓

Store session data in Redis with session ID as key

↓

User makes requests with session ID

↓

Retrieve session data from Redis using session ID

↓

Validate session and respond

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Session expires or user logs out -> Delete session data

This flow shows how a session ID is created, stored in Redis with user data, retrieved on requests, and eventually expired or deleted.

Execution Sample

Redis

SET session:12345 "{\"user_id\":1,\"role\":\"admin\"}" EX 3600
GET session:12345
DEL session:12345

Store a session with key 'session:12345', retrieve it, then delete it to end the session.

Execution Table

Step	Command	Action	Result
1	SET session:12345 "{\"user_id\":1,\"role\":\"admin\"}" EX 3600	Store session data with 1 hour expiry	OK
2	GET session:12345	Retrieve session data by key	{"user_id":1,"role":"admin"}
3	DEL session:12345	Delete session data to end session	1
4	GET session:12345	Try to retrieve deleted session	-

💡 Session deleted at step 3, so retrieval at step 4 returns nil (no data).

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4
session:12345	-	{"user_id":1,"role":"admin"}	{"user_id":1,"role":"admin"}	-	-

Key Moments - 2 Insights

Why does GET return nil after DEL command?

Because DEL removes the session key from Redis, so the data no longer exists. See execution_table step 3 and 4.

What does EX 3600 mean in the SET command?

It sets the session to expire automatically after 3600 seconds (1 hour), so Redis deletes it if not manually removed.

Visual Quiz - 3 Questions

Look at the execution_table, what is the result of GET session:12345 at step 2?

A OK

B {"user_id":1,"role":"admin"}

C nil

D 1

💡 Hint

Check the 'Result' column for step 2 in execution_table.

At which step does the session data get deleted?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look at the 'Command' and 'Action' columns to find when DEL is called.

If we remove EX 3600 from SET, what changes in variable_tracker?

A Session never expires automatically

B Session expires automatically after 1 hour

C Session is deleted immediately

D Session data is never stored

💡 Hint

EX sets expiry time; without it, session stays until deleted manually.

Concept Snapshot

Session storage pattern in Redis:
- Generate a unique session ID
- Store session data with SET key value EX seconds
- Retrieve session data with GET key
- Delete session with DEL key
- Expiry (EX) auto-removes session after time
- Used to track user login state efficiently

Full Transcript

The session storage pattern in Redis involves creating a unique session ID when a user logs in. This ID is used as a key to store session data, such as user ID and role, using the SET command with an expiry time (EX) to automatically remove stale sessions. When the user makes requests, the session data is retrieved with GET using the session ID. To end a session, DEL removes the session data. If the session expires or is deleted, GET returns nil indicating no session found. This pattern helps manage user sessions efficiently and securely.