I don't have a technology stack. Do you just mean what am I using for current projects?

At work we use Rust primarily for services. It was chosen because we're doing a lot of low level and performance sensitive work. The risk we discussed most was devs not knowing the language, which we decided to hedge against in various ways and accepted that risk.

We use Postgres for a lot of data. We've used it a ton at the company and have a lot of expertise. It handles relational data well, Row Level Security helps us with our multitenancy goals, etc. We discussed some risks, like write load on the db, and have mitigations in place for that that I don't want to get into much.

We use gVisor for isolation. This was a more novel pick for us but we had very strict security requirements and the only two options we considered viable were Firecracker and gVisor - we didn't want to require KVM/ hardware support so we went with gVisor and have been very happy with it. There was a sort of "bake off" to evaluate solutions here.

In every case we simply determined our requirements based on product features we needed and decided what to use. Surely we'll regret making a decision eventually but we've had reasons for these decisions every step of the way.