SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a31ac2ac0e4e4c43b472d15cba8602ff671b018ea97f5a9ddd0db87c1d88e148' 
  AND token = 'wKGTM4+IqqfbM/ZGjK8yLzxLuBudqS+gqKxvM/AtPd8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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