[jsty]

Major incidents aside, I always think that cache-related bugs are some of the most likely to go undetected since if you don't test for them end-to-end, they're really not that easy to spot & diagnose.

An article sticking around too long on the home page. Semi-stale data creeping into your pipeline. Someone's security token being accepted post-revocation. All really hard to spot unless (1) you're explicitly looking, or (2) manure hits the fan.

[daper]

I categorize this as bugs caused by data inconsistency because od data duplication. That includes:

- Using asynchronous database replication and reading data from database slaves - Duplicating same data over multiple database tables (possibly for performance reasons) - Having additional system that duplicates some data. For example: in the middle of rewriting some legacy system - a process that was split into phases so functionality between new and old systems overlap for some period of time.

Based on my experience I always assume that inconsistency is unavoidable when the same information is stored in more than one place.

[rightbyte]

Microsoft has some serious problem with token caching. I changed job last month and for two three weeks I could log into my old work account for a split second before being thrown out. (By habit visited the page). I could see the news feed and mails but not long enought to see if they were stale.