Redis as cache vs data store vs message broker - Visual Side-by-Side Comparison

Concept Flow - Redis as cache vs data store vs message broker

Client Request

↓

Cache

↓

Fast Read

↓

Return Data

Client sends request; Redis handles it differently based on use: cache for fast reads, data store for persistence, or message broker for communication.

Execution Sample

Redis

SET user:1 "Alice"
GET user:1
PUBLISH channel1 "Hello"
SUBSCRIBE channel1

Shows Redis commands used as cache (SET/GET), data store (SET/GET), and message broker (PUBLISH/SUBSCRIBE).

Execution Table

Step	Command	Action	Redis Role	Result
1	SET user:1 "Alice"	Store key-value	Cache/Data Store	OK
2	GET user:1	Retrieve value	Cache/Data Store	"Alice"
3	PUBLISH channel1 "Hello"	Send message	Message Broker	Number of subscribers notified
4	SUBSCRIBE channel1	Listen to messages	Message Broker	Subscribed to channel1
5	GET user:2	Retrieve missing key	Cache/Data Store	nil
6	END	No more commands	-	-

💡 Execution stops after all commands processed.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	Final
user:1	nil	"Alice"	"Alice"	"Alice"	"Alice"	"Alice"
channel1_subscribed	false	false	false	false	true	true

Key Moments - 2 Insights

Why does GET user:2 return nil in step 5?

Because user:2 was never set, Redis returns nil indicating no data found, as shown in execution_table row 5.

How does Redis handle PUBLISH and SUBSCRIBE differently from SET and GET?

PUBLISH sends messages to subscribers without storing data, while SET/GET store and retrieve data. This difference is clear in execution_table rows 1-4.

Visual Quiz - 3 Questions

Look at the execution_table, what is the result of the GET command at step 2?

A "Alice"

B nil

C OK

D Error

💡 Hint

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

At which step does Redis subscribe to a channel?

A Step 3

B Step 2

C Step 4

D Step 1

💡 Hint

Look at the 'Command' and 'Action' columns in execution_table for subscription.

If we remove the SET command at step 1, what would GET user:1 return at step 2?

A "Alice"

B nil

C OK

D Error

💡 Hint

Refer to variable_tracker for user:1 value before and after step 1.

Concept Snapshot

Redis can be used in three main ways:
- Cache: temporary fast storage using SET/GET
- Data Store: persistent key-value storage
- Message Broker: send/receive messages with PUBLISH/SUBSCRIBE
Each use changes how Redis handles commands and data flow.

Full Transcript

This visual execution shows how Redis works differently as a cache, data store, and message broker. Commands like SET and GET store and retrieve data for cache or data store roles. PUBLISH and SUBSCRIBE handle messaging without storing data. The execution table traces each command step-by-step, showing results and state changes. Variable tracking shows key values and subscription status. Key moments clarify why missing keys return nil and how messaging differs from data storage. The quiz tests understanding of command results and Redis roles.