OverDrive API Partners,
On 01-DEC-2015, we will release a change in behavior to our Checkouts API. In our current design, the OverDrive Checkouts API returns an HTTP 400 response if either the request to check out (borrow) the title or the request to lock a particular format fails to complete. The new behavior for the OverDrive Checkouts API will be to issue an HTTP 400 response only when the request to check out (borrow) the title fails. We will no longer issue an error response on failed attempts to lock in a particular format during checkout.
What this means for your integration: If you are currently expecting or relying on an HTTP 400 response for failed format lock-ins during the checkout request, you will need to use the Checkouts API response to identify whether a format was locked in during the checkout request. In the event of a failed request to lock a format, the Checkouts API will respond accurately to let you know that the checkout succeeded but no format was locked in during the transaction.
Current documentation for the Checkouts API can be found here.
Thanks for being an OverDrive API Partner.
-The OverDrive API Team