delete-transients-by-prefix.php

<?php

/**
 * Delete all transients from the database whose keys have a specific prefix.
 *
 * @param string $prefix The prefix. Example: 'my_cool_transient_'.
 */
function delete_transients_with_prefix( $prefix ) {
	foreach ( get_transient_keys_with_prefix( $prefix ) as $key ) {
		delete_transient( $key );
	}
}

/**
 * Gets all transient keys in the database with a specific prefix.
 *
 * Note that this doesn't work for sites that use a persistent object
 * cache, since in that case, transients are stored in memory.
 *
 * @param  string $prefix Prefix to search for.
 * @return array          Transient keys with prefix, or empty array on error.
 */
function get_transient_keys_with_prefix( $prefix ) {
	global $wpdb;

	$prefix = $wpdb->esc_like( '_transient_' . $prefix );
	$sql    = "SELECT `option_name` FROM $wpdb->options WHERE `option_name` LIKE '%s'";
	$keys   = $wpdb->get_results( $wpdb->prepare( $sql, $prefix . '%' ), ARRAY_A );

	if ( is_wp_error( $keys ) ) {
		return [];
	}

	return array_map( function( $key ) {
		// Remove '_transient_' from the option name.
		return substr( $key['option_name'], strlen( '_transient_' ) );
	}, $keys );
}

Just found this via a quick google search and it's exactly what I need. Working well. Thanks!