What is the default value for heartbeat.interval.ms?

• A. 1 second
• B. 3 seconds
• C. 5 seconds
• D. 10 seconds

Answer: (B)

Heartbeats keep a consumer’s session alive while it processes records in a group. The frequency is controlled by heartbeat.interval.ms, measured in milliseconds. The default is 3,000 ms, so heartbeats are sent about every three seconds. This works with session.timeout.ms, which defines how long the broker waits without a heartbeat before considering the consumer dead. With a typical default session timeout of 10,000 ms, the three-second heartbeat provides several chances to heartbeat before the session would timeout. If the heartbeat interval is set too long, the broker may miss heartbeats and trigger a rebalance; if it’s too short, you add more heartbeat overhead. The three-second default is a balanced choice.