When we sync, we download all changed history. On first sync, we download all history. We used to do that in one request with a huge payload. We now do that incrementally (Bug 1168856), but -- in order to work with the Sync protocol -- we do so from oldest to newest. If you have a lot of history on the server, this might mean that your most frecent sites don't arrive until we've grabbed 20+ batches. We also keep syncing batches until we're done, so we block subsequent collections from syncing. To address these two things, I propose: -- * If we haven't synced history before, grab a single batch, limit=100, newest-first, and don't track any metadata. * Don't sync the rest of your history on first sync. * Queue up another sync for 30 seconds after the first sync finishes. -- I'll file another bug to think about big bookmark collections.