Hey @RikG, you are correct.  The way errors are communicated is dependent on the configured FlushMode.  In your example the FlushMode is not set, so it's the default of AUTO_FLUSH_SYNC.  In AUTO_FLUSH_SYNC mode any per-row errors are immediately returned as part of the OperationResponse, since the write happens synchronously.  In AUTO_FLUSH_BACKGROUND mode it's necessary to call getPendingErrors.  The docs on AUTO_FLUSH_BACKGROUND cover this to some extent. ... View more