Caching strategies in Wordpress - Step-by-Step Execution

Concept Flow - Caching strategies

User requests page

↓

Check cache storage

↓

Cache hit?

No→Generate page dynamically

↓

Store page in cache

↓

Serve cached page

↓

User sees page quickly

This flow shows how WordPress checks for cached content before generating pages, speeding up response by serving stored pages when available.

Execution Sample

Wordpress

<?php
if ( $content = wp_cache_get( 'homepage' ) ) {
  echo $content;
} else {
  $content = generate_homepage();
  wp_cache_set( 'homepage', $content );
  echo $content;
}
?>

This code tries to get the homepage from cache; if missing, it generates, caches, and displays it.

Execution Table

Step	Action	Cache Check Result	Page Content	Cache Update	Output
1	Check cache for 'homepage'	Miss	N/A	No	No output yet
2	Generate homepage content	N/A	<html>Home</html>	No	No output yet
3	Store generated content in cache	N/A	<html>Home</html>	Cache set with homepage content	No output yet
4	Echo content	N/A	<html>Home</html>	No	Page displayed to user
5	Next request: Check cache for 'homepage'	Hit	<html>Home</html>	No	Page displayed to user from cache

💡 Execution stops after serving cached page or generated page to user.

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	After Step 5
cache_content	null	null	<html>Home</html>	<html>Home</html>	<html>Home</html>
$content	undefined	<html>Home</html>	<html>Home</html>	<html>Home</html>	undefined

Key Moments - 2 Insights

Why does the code check the cache twice with wp_cache_get?

The first check tests if cached content exists (Step 1). The second call retrieves the cached content to output it (Step 5). This avoids generating content unnecessarily.

What happens if the cache is empty or expired?

As shown in Step 1, a cache miss triggers dynamic page generation (Step 2), then the new content is stored in cache (Step 3) for future fast access.

Visual Quiz - 3 Questions

Look at the execution table, what is the cache check result at Step 1?

A Miss

B Expired

C Hit

D Not checked

💡 Hint

See 'Cache Check Result' column at Step 1 in execution_table

At which step is the page content stored in cache?

A Step 2

B Step 3

C Step 4

D Step 5

💡 Hint

Look at 'Cache Update' column in execution_table

If the cache always hits, which steps would be skipped?

A Steps 1 and 5

B Step 4 only

C Steps 2 and 3

D No steps skipped

💡 Hint

Check what happens on cache hit vs miss in execution_table rows

Concept Snapshot

Caching strategies in WordPress:
- Check cache before generating page
- If cache miss, generate and store page
- Serve cached page on hits
- Speeds up page load by avoiding repeated work
- Use wp_cache_get and wp_cache_set functions

Full Transcript

This visual execution shows how WordPress caching works step-by-step. When a user requests a page, WordPress first checks if the page is in cache. If the cache is empty or expired, WordPress generates the page content dynamically, stores it in cache, then serves it to the user. On subsequent requests, WordPress finds the cached page and serves it immediately, skipping generation. Variables like cache_content and $content track the stored and displayed page content. Key moments include understanding why cache is checked twice and what happens on cache misses. The quiz tests knowledge of cache hits, misses, and which steps run in each case.

Practice

1. What is the main purpose of caching in WordPress?

easy

A. To speed up the website by saving copies of pages or data

B. To increase the size of the website database

C. To delete old posts automatically

D. To change the website theme dynamically

Solution

1. Step 1: Understand caching concept

   Caching stores copies of pages or data to avoid repeated processing.

2. Step 2: Identify caching benefit

   By saving copies, the website loads faster for visitors.

3. Final Answer:

   To speed up the website by saving copies of pages or data -> Option A

4. Quick Check:

   Caching = Speed up site [OK]

Hint: Caching saves copies to load pages faster [OK]

Common Mistakes:

• Thinking caching deletes content
• Believing caching increases database size
• Confusing caching with theme changes

2. Which of the following is the correct way to clear the WordPress cache using a plugin?

easy

A. Change the site URL in settings

B. Click the 'Clear Cache' button in the caching plugin settings

C. Delete all posts from the dashboard

D. Deactivate all plugins except caching

Solution

1. Step 1: Identify cache clearing method

   Caching plugins provide a 'Clear Cache' button to remove saved copies.

2. Step 2: Recognize incorrect options

   Deleting posts, changing URL, or deactivating plugins do not clear cache properly.

3. Final Answer:

   Click the 'Clear Cache' button in the caching plugin settings -> Option B

4. Quick Check:

   Clear cache = Use plugin button [OK]

Hint: Use plugin's clear cache button to refresh content [OK]

Common Mistakes:

• Deleting posts thinking it clears cache
• Changing site URL to fix cache
• Deactivating unrelated plugins

3. Consider this code snippet in a WordPress theme's functions.php file:

function get_cached_data() {
  $cache_key = 'my_data';
  $data = wp_cache_get($cache_key);
  if ($data === false) {
    $data = 'Expensive data';
    wp_cache_set($cache_key, $data, '', 3600);
  }
  return $data;
}

echo get_cached_data();

What will this code output on the first call?

medium

A. An error message

B. false

C. null

D. Expensive data

Solution

1. Step 1: Check cache retrieval

   On first call, wp_cache_get returns false because cache is empty.

2. Step 2: Set and return data

   Since cache is empty, 'Expensive data' is set and returned.

3. Final Answer:

   Expensive data -> Option D

4. Quick Check:

   First call returns new data [OK]

Hint: First cache get returns false, so data is set and returned [OK]

Common Mistakes:

• Assuming cache returns null instead of false
• Expecting error on missing cache
• Thinking cache returns old data on first call

4. You added caching to your WordPress site, but after updating content, visitors still see old pages. What is the likely problem?

medium

A. The site URL is incorrect

B. The theme is incompatible with WordPress

C. Cache was not cleared after content update

D. The database is corrupted

Solution

1. Step 1: Understand caching effect

   Caching saves old page copies to speed up loading.

2. Step 2: Identify update issue

   If cache is not cleared after content changes, old pages show to visitors.

3. Final Answer:

   Cache was not cleared after content update -> Option C

4. Quick Check:

   Old pages = Cache not cleared [OK]

Hint: Always clear cache after content updates [OK]

Common Mistakes:

• Blaming theme for caching issues
• Assuming database corruption causes old pages
• Thinking site URL affects caching

5. You want to improve your WordPress site's speed by caching database query results for 10 minutes. Which approach is best?

hard

A. Use wp_cache_set() with a 600-second expiration after fetching query results

B. Disable all caching plugins and rely on browser cache only

C. Manually save query results in a text file and read it each time

D. Increase PHP memory limit to store all queries in RAM

Solution

1. Step 1: Identify caching method for query results

   wp_cache_set() stores data in WordPress object cache with expiration time.

2. Step 2: Set expiration for 10 minutes

   600 seconds equals 10 minutes, so setting expiration to 600 caches results properly.

3. Step 3: Evaluate other options

   Disabling plugins loses caching benefits; manual file saves are inefficient; increasing memory doesn't cache queries automatically.

4. Final Answer:

   Use wp_cache_set() with a 600-second expiration after fetching query results -> Option A

5. Quick Check:

   Cache query with wp_cache_set + 600s [OK]

Hint: Use wp_cache_set with expiration for timed caching [OK]

Common Mistakes:

• Disabling caching plugins thinking it helps
• Trying manual file caching instead of built-in cache
• Increasing memory without caching logic