Comment by woile

Thanks! This example uses nearby-joins (based on event time): https://slipstream.readthedocs.io/en/1.0.1/cookbook.html#joi....

I hope I get your question right, but if you're joining on a fixed key, the solution should be simpler. If the data is partitioned by id (partition 0 has id's 0 - 9, and 1 has 10 - 19), each message still passes through the handler that stores each message in the cache. So in the cache it will no longer be partitioned. Let's say each weather update has a fixed `id` we could join on, we'd simply use the following logic instead:

``` if w := weather_cache[id]: return f'The weather during {a["value"]} was {w["value"]}'

return a['value'], '?' ```

It may be the case that the weather updates come in late, in which case we may be joining with stale data. For that we can use Synchronization: https://slipstream.readthedocs.io/en/1.0.1/cookbook.html#syn...

Here's a full example that sends out corrections: https://gist.github.com/Menziess/22d8a511f61c04a8142d81510a0...

Instead, you could also wait by pausing the activity stream by setting the Checkpoints Dependeny downtime_threshold to 0. Perhaps negative values may also work, although I haven't tried yet.