Hello Erik
The failover time you’re experiencing is quite normal for an ASA Active/Stafailover setup. The ASA failover process involves several steps such as checking the health of the units, transferring the stateful information, and switching the active role, which can take some time.
However, you can adjust some of the failover criteria to attempt to get a faster failover time. For example, you can adjust the failover poll time (the time ASA waits before declaring the other unit as failed) using the failover polltime command. Keep in mind that setting this value too low can cause unnecessary failover. You can also use BFD to help improve failover times, but BFD is only supported on firepower 9300 and 4100.
You should be careful when adjusting these parameters as they can cause unexpected results. For more information about these configs, take a look at the following Cisco documentation:
Remember, the goal of failover is not to provide zero downtime, but to provide a backup in case the primary system fails. If you need a higher level of availability, consider using an Active/Active arrangement.
I hope this has been helpful!
Laz