How to find the space when a user PUTs a CAR

[olizilla]

We will want to be able to show when a store/add is pending vs we have actually got the CAR.

The store/add dynamo table is currently partitioned by space DID, and the car CID is the sort key, so we enforce a unique car per space. This makes it cheap to find all cars for a space and terrible for finding a space by car CID.

We need some way to connect the ObjectCreated event we get from S3 back to the store/add invocation that enabled it.

Of note, we will need to handle the case where multiple independent store/add invocations are made for the same shard cid. We only skip providing a presigned url once an upload is fully written to s3. multiple callers could start writing at the same time.

[olizilla]

The proposal that @Gozala re-shared is to write the store/add invocation to a bucket prefixed with the car cid like /${carCid}/${invocationCid}... so when we get an S3 ObjectCreated event we can go and list all the keys that start with the carCID to find the 1 or more invocations that got it there.

Alternatives are

• another dynamo table keyed by carCid (same idea but state in a db)
• a redis (same idea but state in a fast store)
• encode the space or invocation CID into metadata in the query string in the presigned PUT URL.
  • the later is possible, but would need to prove that we get the metadata in the S3 event to deal with the case where the same shard is PUT from two different store/add invocations.

[olizilla]

or we could add global secondary index on the the store/add table to let us find spaces by car.

{ partitionKey: 'link', sortKey: 'space' }