How to check if a given question is changed

Question

What is the fastest way to check if a question is changed using the API calls?
For my purpose (a cache), a question is considered changed if:

• A new comment is added to the question or to any of its answers
• It had any new activity

What is the fastest way to get this check?

^{* the check should work also for questions with hundreds of answers}

Answer 1

I have been working on another API recently so I may be a bit dull but my first impression is that the path of least resistance is to

• pull your question(s) with answers and comments disregarding activity/creation filter (use max page size)
• compare last activity date of the question. this will include new answers and edits on both the question and answers - if bumped you have your answer - pass go
• compare comment count on the question and then each answer - if any have changed you have your answer - pass go
  • an obvious but unlikely hole here is if a comment is deleted and a comment is added resulting in an unchanged comment count. If this is a concern, compare comment_id

In terms of efficiency, this entails 1 (large payload) request and single iterated nested control structure for up to 100 questions ^*. One advantage is that if you pull with body=true, you already have your updated information.

Not as efficient as a last_activity_date that included comment activity but you work with what you have.

^{* This will likely break down for abnormal posts that contain >100 answers or posts with >100 comments. The only way I have found to fetch these is to perform distinct multipage pulls for answers and comments for each question, to which you would then apply the above criteria.}