[New Feature]: Allow TTL attribute to also be a partition or sort key

[MartinRamm]

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[ryanblock]

Does DynamoDB actually support this? Why would one want to do this? It seems like kind of a bad idea for quite a few reasons.

[MartinRamm]

Does DynamoDB actually support this? Why would one want to do this? It seems like kind of a bad idea for quite a few reasons.

I got no errors when adding TTL as a sort key on AWS. While I agree that it might be a bad idea to make TTL the primary key, I don't see why making it a sort key is a bad. Could you explain please?

[ryanblock]

Getting no errors adding TTL as sort key doesn't mean it will actually work, but let's say for the sake of conversation that it does work. A few reasons that come to mind:

• This does not generally abide by the principle of separation of concerns
• TTL resolution is in seconds, not ms, so it's a pretty poor sort key
• Keys cannot be mutated, so if you need to extend the TTL (say for a session or what have you), you must destroy the old item and create a new one
• This behavior is, as far as I can tell, not documented; as such, I'm not confident it can be counted to work indefinitely. This could simply be a case that DynamoDB hasn't accounted for yet and they may disable it in the future – I'm just not sure!
• As Architect is concerned, it's mixing metaphors (TTL is one thing, sort keys are another thing)

I'm still wondering what the necessity is here!

[ryanblock]

@MartinRamm chatted some more about this internally and it was mentioned that maybe the goal here is to enable querying by something that will expire by a certain time? Was that the use case? Would love to hear more about what you're aiming to build with this functionality.

Anyway, I think we can get there with additions to documentation in https://github.com/architect/arc.codes

Thanks!