When searching or indexing, you might run into an error stating
The Acquia Search flood control mechanism has blocked a Solr query due to API usage limits
This is due to the default flood control limitations that come pre-shipped with Acquia Search. Fortunately those configurations can be changed.
Following the below instructions and overriding the limits to a high value may result in your application's usage exceeding your contractual limits. If this happens you may contacted by our Account Management/Sales team to discuss an entitlement and billing increase, or in extreme cases, your shared Search service could be temporarily disabled to keep platform integrity. See our Acquia Search Product Guide: Entitlements and Acquia Search Documentation: Staying under limits pages or more information.
Depending on the scenario where you encounter this error, you might want to tackle this issue in different ways.
The "catch-all" way of dealing with this issue would be to increase those flood control limit values. However, there is a different configuration for each type of query. That means that /select queries can have a different value with regards to flood control limits compared to /update queries.
If you are running into the error while searching, then you would want to increase the /select limit as such, "200" being an example value
drush --uri=www.example.com cset acquia_search.settings flood_limit.select.limit 200
If on the other hand you are running into the error while indexing, you could either increase the flood control limit for update requests - again "1000" is an example value
drush --uri=www.example.com cset acquia_search.settings flood_limit.update.limit 1000
... or, for this scenario, you could also increase the amount of entities processed in each batch, thus making the requests less frequent, but with a larger payload; If you do that you might not have to tweak the flood control limitation.
When using drush to index you can use --batch-size to achieve that
# Index in batches of 500. Note: if you run out of memory, use smaller batches. drush --uri=www.example.com search-api:index --batch-size=500
See our Acquia Search Documentation: Staying under limits document page.