SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '31bc8d4f189f73aa8fb10d35c9cccafd6c7dbe68d3ebe13284288786435ce628' 
  AND token = 'gGa/+1TbkjU+8D7ILtreuOIrN7OOyKUw7gLOqCpbM1o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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