Are there any WORM (write once, read many) data stores that integrate well with Rails?

I've gotta store a bunch of events, which are snippets of data that contain information about a thing that happened inside the system I'm working on. I'm building out audit trail, which could potentially be used in legal proceedings.

There are a couple predominant things I'll need to be able to achieve with them:

• Lots of searching, filtering, sorting and slicing by various attributes stored inside
• csv exporting (wouldn't be a real feature if we didn't need to export to csv!)
• They'll need to be stored and accessible for a minimum of a year (possibly 3)

And then, not a necessity but would be cool,

• verify if the data was tampered or not w/ a hash

Currently it's safe to say that, the data model for these events isn't settled.

{
  "name": "some_predefined_event_name",
    "true_tstamp": "some tzinfo value",
    "traits":
     {
       "user_id": 346,
        "investment_id: 256,
        "arbitrary": "json"
     }
}

The best looking approach so far seems to involve longer-term storage on AWS Glacier, as that will tick the compliance boxes, but that leaves the shorter-term needs like searching & filtering, csv generation, unfulfilled.

Or maybe somehow disabling anything but writing and reading in DynamoDB via IAM policies, then taking the monthly chunks of that and moving them over to Glacier.

Is there a better way to go at this?