Implementing a license key management system on GAE: Datastore or Cloud SQL?

Question

I am implementing a license key system on Google AppEngine. Keys are generated ahead of time and emailed to users. Then they log into the system and enter the key to activate a product.

I could have potentially several hundred people submitting their keys for validation at the same time. I need the transactions to be strongly consistent so that the same license key cannot be used more than once.

Option 1: Use the datastore

To use the datastore, I need it to be strongly consistent, so I will use an EntityGroup for the license keys. However, there is a limit of 1 write / second to an entity group. Appengine requests must complete within 60 seconds, so this would mean either notifying users offline when their key was activated, or having them poll in a loop until their key was accepted.

Option 2: Use Google Cloud SQL

Even the smallest tier of Google Cloud SQL can handle 250 concurrent connections. I don't expect these queries to take very long. This seems like it would be a lot faster and would handle hundreds or thousands of simultaneous license key requests without any issues.

The downside to Google Cloud SQL is that it is limited in size to 500GB per instance. If I run out of space, I'll have to create a new database instance and then query both for the submitted license key. I think it will be a long time before I use up that 500GB and it looks like you can even increase the size by contacting Google.

Seems like Option2 is the way to go - but I'm wondering what others think. Do you find Entity Group performance for transactions acceptable?

Answer 1

I will go with Option 1 datastore, it's much faster and scalable.

And I don't know why you need to create EntityGroup, you could make the "license key" itself as the Key, so each Entity is in it's own EntityGroup... only this will make things scalable.

Answer 2

Option 2 seems more feasible, neat and clean in your case but you have to take care of db connections by yourself and its a hassle with increasing load if connection pooling is not properly used.

Datastore can also be used in license key system by defining multiple EntityGroups with dummy ancestors based on few leading or trailing digits of key to deal with 1 write / second to an entity group. In this way you can also easily determine EntityGroup of a generated or provided license key.

For example 4321 G42T 531P 8922 is license key so 4321 can be used as EntityGroup and all keys starting with 4321 will be part of this EntityGroup. This is sort of sharding like mechanism to avoid the potential of simultaneous writes to single entity group.

If you need to perform queries on some columns other than license key then a separate mapping table can be maintained without an EntityGroup.

Answer 3

You can mixed them , Google Cloud SQL is only have Keys and Email , with 500G i belived you can store key for all of people in the planet . In other hand you can request google to increase data size limit .