This will be a self-answered question. It doesn't appear to be in answers anywhere, so I'm adding it myself.
When updating a collection, if you exceed the limit of entries in one request, you will receive this error:
Request exceeds API limits - see limits.conf for details. (Too many documents for a single batch save.)
What is the default limit? What are the stanza and key to change it?
The limit is controlled by the kvstore stanza in limits.conf. The key is max_queries_per_batch.
max_queries_per_batch = 1000
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