Impelementing aging in a Firebase real time database

Question

Unfortunately, Firebase doesn't have out of the box an aging mechanism (delete old entries automatically). So, I am trying to implement one. However, I am stuck between two decisions:

1. If a client fetch an old entry, he will delete automatically: I think it is the easiest for my context, but it doesn't look very secure to me.
2. Implement a small script/program on a server that will check the full database and delete old entries.

I like the first solution, since it doesn't include deploying another server side application but I don't know if it could represent a risk.

What do you think is the best ? How can I secure the first solution to avoid any possible deletion of all items ? For the second solution, I don't won't to run the script from my computer and I don't want to pay for another sever to deploy the script, it it possible to to deploy it on Firebase ?

Answer 1

Deleting outdated items from the client has been covered before. See:

• Firebase chat - removing old messages
• How to delete firebase data after "n" days
• Delete firebase data older than 2 hours

To secure this operation so that only outdated items can be removed, you can use Firebase Database security rules. Something like:

{
  "rules": {
    "messages": {
      "$message": {
        // only messages older than an hours can be remove
        ".write": "newData.exists() || data.child('timestamp').val() < (now - 3600000)",
      }
    }
  }
}

Running your own code on Firebase's servers can now be done with Cloud Functions for Firebase. There is also a sample that shows how to delete older data with Cloud Functions.