SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '347a664e8066b915327a8aafb45483452eaccdb3e290ef9a3b90996340eed3c9' 
  AND token = '6veWM/uZnVErTBvV0Zz5SNwi5yrvnGQZbdh6rFOTJvo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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