The disclosure is directed to failover mechanisms in a distributed computing system. A region of data is managed by multiple region servers. One of the region servers is elected as a “leader” and the remaining are “followers.” The leader serves the read/write requests from a client. The leader writes the data received from the client into the in-memory store and a local write-ahead log (“WAL”), and synchronously replicates the WAL to the followers. A region server designated as an “active” region server synchronizes a distributed data store with the data from the WAL. Active witness followers apply the data from the WAL to their in-memory store while shadow witness followers do not. Different types of servers provide failover mechanisms with different characteristics. A leader is elected based on their associated ranks—higher the rank, higher the likelihood of electing itself as a leader.