I worked for TMobile for 4 days in 2021. I don't usually apply to big companies but money was tight because pandemic and I needed a job quick. I was assigned to work on the config server (think in-house developed consul or etcd) and it was awful. "If this specific config value is being set by Service A then what is actually written should be twice the given value, but if Service B is reading the value, return 1/3 of the value as an HTTP form body instead of JSON." By Thursday I got a call about a new position and I left so quick that the recruiters black listed me. TMobile getting hacked is a "when" not an "if"