1. Typos in Separate Documents by Granularity Level:

"This introduce a second set of upsert operations to the data collection and aggregation portion of your application but the gains reduction in disk seeks on the queries, should be worth the costs. Consider the following example schema:"

Perhaps:

"This introduces a second set of upsert operations to the data collection and aggregation portion of your application, but the reduction in disk seeks on the queries should be worth the costs. Consider the following example schema:"

2. Later in the Sharding section:

"This is basically unavoidable, since all updates for a single page are going to a single document."

3. Also this awkward sentence:

"You may wish to include the date in addition to the site, and page fields so that MongoDB can split histories so that you can serve different historical ranges with different shards."

Perhaps:

"You may wish to include the date in addition to the site and page fields so that MongoDB can split histories and serve different historical ranges with different shards."