SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f8191ebb88fe0023f9a31fe08019e3ddfcc58590b5979d9669ab2e37be9a67b6' 
  AND token = 'nUqbbwclHJ80lxLhqnvXQxLcvHjmYuw1tdOkL2007Bs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00055

JSON explain

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