Cryptocurrency transactions are irreversible, so it's critical to have strong security protocols in place. Once you lose cryptocurrency it's gone for good.
A huge part of our strategy is surprisingly non-technical: we store the vast majority of our crypto in secure locations with no access to the internet. We also back up our keys in a distributed manner, meaning there are multiple redundancies in place to prevent accidental loss.
We don't store any crypto at our office whatsoever, and only a small amount of it ever touches our servers to facilitate withdrawals. So even if an intruder did manage to get access to our hot wallet, they would find such a small amount of crypto there as to make it not worth the effort.