Cache warming strategies in Redis - Step-by-Step Execution

Concept Flow - Cache warming strategies

Start: Cache is cold

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Identify critical data

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Preload data into cache

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Serve requests from cache

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Monitor cache hits/misses

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Update cache as needed

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Repeat preload periodically or on triggers

Cache warming loads important data into Redis before requests arrive to reduce delays and improve performance.

Execution Sample

Redis

SET user:1 "Alice"
SET user:2 "Bob"
GET user:1
GET user:3

This example preloads two user keys into Redis, then retrieves one existing and one missing key.

Execution Table

Step	Command	Action	Cache State	Output
1	SET user:1 "Alice"	Store key user:1 with value "Alice"	{"user:1":"Alice"}	OK
2	SET user:2 "Bob"	Store key user:2 with value "Bob"	{"user:1":"Alice", "user:2":"Bob"}	OK
3	GET user:1	Retrieve value for key user:1	{"user:1":"Alice", "user:2":"Bob"}	"Alice"
4	GET user:3	Attempt to retrieve missing key user:3	{"user:1":"Alice", "user:2":"Bob"}	(nil)

💡 Finished commands; user:3 not found in cache (cache miss).

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4
Cache	{}	{"user:1":"Alice"}	{"user:1":"Alice", "user:2":"Bob"}	{"user:1":"Alice", "user:2":"Bob"}	{"user:1":"Alice", "user:2":"Bob"}
Output	N/A	OK	OK	"Alice"	(nil)

Key Moments - 2 Insights

Why does GET user:3 return nil even after warming the cache?

Because user:3 was never preloaded into the cache (see execution_table step 4), so Redis returns nil indicating a cache miss.

Does warming the cache guarantee all requested data is in cache?

No, warming only preloads selected keys (see steps 1 and 2). If a key wasn't preloaded, a GET will miss (step 4).

Visual Quiz - 3 Questions

Look at the execution_table at step 2, what is the cache state?

A {"user:1":"Alice", "user:2":"Bob"}

B {"user:1":"Alice"}

C {}

D {"user:2":"Bob"}

💡 Hint

Check the Cache State column at step 2 in execution_table.

At which step does the cache miss occur?

A Step 1

B Step 3

C Step 4

D No cache miss

💡 Hint

Look at the Output column for '(nil)' indicating a miss in execution_table.

If we preload user:3 with SET user:3 "Carol" before step 3, what would GET user:3 return?

A (nil)

B "Carol"

C "Bob"

D Error

💡 Hint

Preloading adds the key to cache, so GET returns its value (see variable_tracker Cache changes).

Concept Snapshot

Cache warming strategies:
- Preload important keys into Redis before requests
- Use SET commands to load data
- Reduces cache misses and latency
- Monitor cache hits to adjust warming
- Not all keys must be preloaded
- Helps improve app performance

Full Transcript

Cache warming strategies in Redis involve loading important data into the cache before it is requested. This reduces delays caused by cache misses. The flow starts with a cold cache, then critical data is identified and preloaded using SET commands. Requests then retrieve data from cache with GET commands. Monitoring cache hits and misses helps decide when to update the cache. In the example, keys user:1 and user:2 are preloaded. Retrieving user:1 returns its value, but user:3 returns nil because it was not preloaded. This shows warming improves cache hits but does not guarantee all keys are cached.