SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a5a323808e7f3accb2f551f857d274f249fb6bc21962152a10c704bc488e9eb1' 
  AND token = 'UMISO2RINBKu/obdhz9wyshb0TO729NVI8rr7rCS2S8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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