I worked at Fidelity in multiple BUs and teams.
Finally moved to FBT (Brokerage Technology) and the nightmare started.
If you hear FBT or NextGen or Platform Services then please avoid this organization for your own good. The culture is even worse than service based companies. Few folks in the team micromanage to the next level. They will ping you on teams/whatsapp at 12am-1am asking to do things while they themselves are unavailable throughout the day. The team is filled with inexperienced, arrogant freshers who tend to show that they know everything. You will spend most of your time correcting others mistakes or hand holding juniors.
They make you work till late nights, weekends and during appraisal will only point out random things and give you single digit increment.
They do have several reporting mechanisms but since the team is mostly filled with freshers they do not report anything to senior management in fear. There is lot of favouritism, even if you join, there are couple of people in the team who would be appreciated even for reaching the office while you doing the toughest job will be brushed under the rug.
Tech stack is very basic, in 3 months you will learn pretty much everything and then it is an endless loop of doing the same thing over and again.