SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c6fa5965c7ef5428fccd7e42b81dbf3b3fe89f54109174379213105ba0774a7f' 
  AND token = 'ST+rKtm6wz/z9qirFnUC/aFy6YlOfWhSR56Y3QwBLwQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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