Test your knowledge

Let's see whether you can answer the following questions correctly:

1. QoS level 0 for MQTT means:
   1. Exactly once delivery
   2. At most once delivery
   3. At least once delivery
2. QoS level 1 for MQTT means:
   1. Exactly once delivery
   2. At most once delivery
   3. At least once delivery
3. QoS level 2 for MQTT means:
   1. Exactly once delivery
   2. At most once delivery
   3. At least once delivery
4. If the application isn't able to tolerate duplicates and we have to make sure that the messages reach the subscribers only once, the appropriate choice is:
   1. QoS level 0
   2. QoS level 1
   3. QoS level 2
5. Which QoS level has the highest overhead:
   1. QoS level 0
   2. QoS level 1
   3. QoS level 2

The rights answers are included in the Appendix, Solutions.