SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b5496b84f81bdc5114304d21942d272b72c9a6a45f4593890d6a6b3c552c277d' 
  AND token = 'htLBdI8tqExUXGUGxc1sZul3KYblavclqZezDo8Um5I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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