get_algolia_index_name.php

<?php

add_filter('get_algolia_index_name', 'get_algolia_index_name');

// Filter to construct canonical index names
function get_algolia_index_name($name = '') {
    global $wpdb;
    $env_prefix = getenv('ALGOLIA_INDEX_PREFIX') ?: ''; // local, dev, stage, or prod
    $base_prefix = $wpdb->base_prefix; // wp_
    return "${env_prefix}_${base_prefix}${name}";
}

// When ALGOLIA_INDEX_PREFIX=local, this ends up being `local_wp_global_search`
$canonical_index_name = apply_filters('get_algolia_index_name', 'global_search');

// Then init the `local_wp_global_search` index
$global_index = $algolia->initIndex($canonical_index_name);