> [...] the maintenance headaches with MySQL started to have negative effects on our teams morality [...]<p>As a general observation, "morality" (eg moral values) might be the wrong word there. Guessing you're meaning "morale" (?), which is more like "how happy our team members are".<p>That minor nitpick aside though, thanks for sharing. :)
"Cannot online add a new column"
This is false.
<a href="https://dev.mysql.com/doc/refman/5.6/en/innodb-create-index-overview.html#innodb-online-ddl-summary-grid" rel="nofollow">https://dev.mysql.com/doc/refman/5.6/en/innodb-create-index-...</a><p>Very weird.
Interesting read, and jealous somebody gave you 2 years for such migration :)<p>Small point of attention, on Safari/OSX swat.io loads as a white page with a scrollbar (it notices the page is larger in height), but only to be populated with content only 5 to 10 seconds after.
"We had complete lock ups where max_connections was exceeded and we could never find a source, internal or external, to our system. Literally hundreds of connections doing SELECT statements but nothing else. Eventually manually killing them “solved” it"<p>Wouldn't having "max_connections" postgresql processes create more problems?