SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '021ac58d1b832c6875d3e31fa9d625f6fbec2a9f57e8ba2698519d71673d16f5' 
  AND token = 'WJD+A7YMhFUYIKVX5rq/JzGgNyeIPzpZCQpIHTCKwX4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}