Response Slow when Order BY is added to my SQL Query

Question

I have the following job_requests table schema as shown here

+-------------+--------------+------+-----+---------+----------------+
| Field          | Type         | Null | Key | Default | Extra          |
+-------------+--------------+------+-----+---------+----------------+
| id             | int(11)      | NO   | PRI | NULL    | auto_increment |
| available_to.  | integer[]    | NO   |     |         |                |
| available_type | varchar(255) | NO   |     | NULL    |                |
| start_at       | varchar(255) | NO   |     | NULL    |                |
+-------------+--------------+------+-----+---------+----------------+

I have the following query to return a list of records and order them by the type_of_pool value

WITH matching_jobs AS (
        SELECT
            job_requests_with_distance.*,
            CASE WHEN (users.id = ANY (available_to) AND available_type = 0) THEN 'favourite'
            ELSE 'normal'
            END AS type_of_pool
        FROM (
            SELECT
                job_requests.*,
                users.id AS user_id,
    
            FROM
                job_requests,
                users) AS job_requests_with_distance
        LEFT JOIN users ON users.id = user_id
    WHERE start_at > NOW() at time zone 'Asia/Kuala_Lumpur'
        AND user_id = 491
        AND (user_id != ALL(coalesce(unavailable_to, array[]::int[])))
    )
    
    
    SELECT
        *
    FROM
        matching_jobs
    WHERE (type_of_pool != 'normal')::BOOLEAN
    ORDER BY
      array_position (ARRAY['favourite','exclusive','normal']::text[], type_of_pool),
    LIMIT 30

If i remove the ORDER BY function, it takes about 3ms but when I add the ORDER BY function, it takes about 1.3seconds to run.

Not sure how do i optimize this query to make it faster? I have read using Indexes and all but not sure how an index will help in this scenario.

Any help is appreciated.