Each change arrives as a short message: a row was inserted, updated or deleted, here is the key and here is what it looks like now. Postcards from the Change Feed is that stream, read in order by anyone who needs to stay in sync with the source without querying it repeatedly.

Treat the feed as a contract. Know whether messages carry the before and after image, how deletes appear, how schema changes are signaled and what happens when a consumer falls behind. The postcards are only useful if you can sort them.