Note to anybody reading this but not following the link: parent poster means "queue your writes in Redis" and not "query."

I'm sorry, I am not a native speaker and it was already late.

How does snowplow solve this problem? By writing to disk?

Snowplow is implemented as a unidirectional data pipeline:

    tracking -> collection -> enrichment -> storage

Between each step there is typically some kind of persistent queue (mostly S3/Kinesis), and data won't be lost if a downstream component is not operational. Examples:

* If your event collector is unavailable, raw events will be cached in the tracker in localStorage, SQLite or similar

* If your Redshift database is read-only for maintenance, enriched events will be held back until Redshift is writeable again

There is of course the opportunity for a collector to be down, but the aim is to keep those components super simple and rely on really durable storage (Kinesis, S3) managed by someone else.