WordPress Transients Explained

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WordPress has lots of internal tools that can help you to a faster, resource saving version of WordPress. One of those tools is the WordPress Transients API. Making use of this API is something I myself recommending a lot in my performance audits. Which leads me to conclude that the WordPress Transients API is not as well-known as it should be.

WordPress transients play a significant role in caching data and enhancing the performance of a WordPress site. These little helpers take on heavy-lifting tasks in the background, freeing up resources to provide a faster, more enjoyable experience for its users.

What are transients?

Let me explain. Imagine how much time you’d save if the answers to some of your most commonly used queries are readily available, without you having to query for those answers over and over again. That’s exactly the role WordPress Transients play. They’re a form of internal cache that WordPress uses to store temporary data. This internal cache, this transient is expected to expire after a while.

What does this mean?

You might be wondering, what exactly does this mean? Don’t worry, we’ll break it down even further. Think of transients like memos that carry some important details. Instead of going through the time-consuming process of finding these details every time, WordPress refers to these memos. These are stashed away until the information changes or they’re no longer needed.

This process is known as “caching.” This might seem a little confusing if you’re new to the world of WordPress or website development, but it’s actually a pretty simple thing. The purpose of caching is to streamline processes that are repetitive or take a considerable amount of time. It’s this caching method that ensures that WordPress can retrieve data faster and provide a better user experience.

Transients Aren’t Supposed to be Forever

While the primary function of transients is to speed up processes, they aren’t ideal for storing all types of data. This is because transients are temporary. They are designed to ‘expire’ once they’re no longer necessary, making room for new data.

This is why they’re perfect for storing data like the results of complex database queries or remote API calls, but not for critical data that should be permanently stored. If you need to store data longer, then it makes more sense to use the WordPress Options API or Settings API.

In short: The Transients API in WordPress is a feature that allows developers to temporarily store cached data in the database. It is similar to the WordPress Options API, but with an expiration time.

WordPress Transients Use Cases

Transients in WordPress are versatile and can be used in numerous ways. Below are five different use cases with brief code examples:

Use Case 1: Caching API Calls

When you’re retrieving data from an external API, you can store the response in a transient to avoid unnecessary delays for future data retrieval.

// Check for the transient data
$data = get_transient( 'my_special_api_call' );

if ( !$data ) {
    // Transient has expired, so we make an API call
    $response = wp_remote_get( 'https://api.example.com/data' );

    if ( !is_wp_error( $response ) ) {
        $data = json_decode( wp_remote_retrieve_body( $response ) );

        // Cache the API response in a transient for 1 hour
        set_transient( 'my_special_api_call', $data, 60*60 );

Use Case 2: Caching Results of Complex Queries

Storing the result of an elaborate database query in transients can improve performance, as it prevents the need to run the query each time the data is required.

// Check for the transient
$data = get_transient( 'my_complex_query' );

if (!$data) {
    // Create a new WP_Query
    $query = new WP_Query( array( 'post_type' => 'post', 'nopaging' => true ) );

    // Run the query to fetch data
    $data = $query->posts;

    // Cache data in a transient for 24 hours
    set_transient( 'my_complex_query', $data, 24 * 60 * 60 );

Use Case 3: Storing User Sessions

Transients can store user session data, like recently viewed posts or pages.

// Get the transient
$recently_viewed = get_transient( 'recently_viewed' . $user_id );

// If the transient does not exist, initialize it
if ( !$recently_viewed ) {
    $recently_viewed = array();
// Add the current post to the recently viewed posts
array_unshift( $recently_viewed, $current_post_id );

// Update the transient with the new viewed posts
set_transient( 'recently_viewed' . $user_id, $recently_viewed, 60 * 60 );

Use Case 4: Caching Custom Route Data

You can cache custom route data in transients, this can significantly enhance the loading time of WordPress custom routes.

// Check for the transient
$data = get_transient( 'my_custom_route_data' );

if ( !$data ) {
    // Perform complex calculations to get custom route data
    $data = calculate_route_data();

    // Cache the data in a transient for 1 hour
    set_transient( 'my_custom_route_data', $data, 60 * 60 );

Use Case 5: Managing Temporary Notifications

Ephemeral data like temporary admin notifications can be managed using transients.

// Set a transient that exists for 5 minutes
set_transient( 'admin_notice_message', 'This is your message', 5 * 60 );

// Get the transient value
$message = get_transient( 'admin_notice_message' );

if( $message ){
    // Show admin notice
    echo "<div class='notice notice-success is-dismissible'><p>{$message}</p></div>";
    // Delete transient data
    delete_transient( 'admin_notice_message' );

The five varied practical use cases demonstrate the versatility of WordPress transients and show how they can help you in optimizing your website performance. To get the most out out the Transient API, head on over to the full documentation.

There you have it. We’ve just covered the amazing world of WordPress transients, even delving into the stories of how they work.

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