1. Run your own Snowplow collector that writes to your Redshift.
2. Use Snowplow Inc's hosted collector that writes into your Redshift.
3. Use Fivetran's Snowplow collector that writes to your Redshift.
We have customers running each of these configurations. In the case of #1 & 2, they're just using us to sync other data into the same Redshift cluster as their snowplow collector.