Single entry with 450 Matrix blocks throwing error on save A client has a Singles entry with a Matrix block defined that contains a few text fields, and one image field. They've created approximately 450 instances of this Matrix block, and can no longer update the page. Craft throws a 500 error. Craft logs just show a basic 

exception 'Craft\HttpException' in /srv/[clientName]/releases/20170418025256/craft/app/controllers/TemplatesController.php:59

and nothing of use in the Apache error logs. Anyone have experience with this sort of error, or confidence that this would be a Craft bug?
Most likely you're bumping into php.ini limitations.  I'd bump the values of memory_limit, post_max_size and max_input_vars and see if that helps.

They are common culprits when POSTing large amounts of data (which is what 450 Matrix Blocks would be considered).