A company is looking for a hardware feature with the least amount of downtime in terms of firmware upgrades. Which of the following features BEST meet this requirement?

In-service upgrades refer to upgrading a single device while it remains active, which differs from the sequential, cluster-wide approach that rolling upgrades provide across multiple nodes.

Rolling upgrades apply firmware to one node or component at a time while all other nodes continue to serve traffic, ensuring the system as a whole remains available during the upgrade window. This approach is specifically designed for production hardware environments where sustained availability is required, and it results in the least cumulative downtime compared to other upgrade strategies.

Failover upgrades depend on a standby unit taking over while the primary is upgraded, which introduces a failover event and additional recovery steps rather than a seamless sequential process.

User-mode upgrades are not a recognized hardware firmware upgrade category and do not describe any standard mechanism for reducing downtime during firmware deployments.