Topic exchange (pattern matching) in RabbitMQ - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Routing key matching with topic exchange

Given a topic exchange with a binding key stock.*.nyse, which routing key will cause a message to be delivered to the queue?

A stock.tech.nyse

B stock.nyse

C stock.tech.nyse.extra

D stock.nyse.tech

💡 Hint

Remember that * matches exactly one word in the routing key.

The binding key stock.*.nyse matches routing keys with exactly three words where the middle word can be anything. Option A matches this pattern. Option A has only two words, C has four words, and D has the words in the wrong order.

🧠 Conceptual

intermediate

Understanding the '#' wildcard in topic exchanges

What does the # wildcard represent in a RabbitMQ topic exchange binding key?

A Matches only the last word in the routing key

B Matches exactly one word in the routing key

C Matches only the first word in the routing key

D Matches zero or more words in the routing key

💡 Hint

Think about how many words # can match.

The # wildcard matches zero or more words separated by dots in the routing key. It allows flexible matching of multiple words or none.

🔀 Workflow

advanced

Configuring multiple bindings for selective message routing

You want to route messages with routing keys log.error.system and log.error.application to a queue named ErrorLogs. Which binding keys should you use on the topic exchange to achieve this?

A log.error.*

B log.*.error

C log.#.error

D *.error.*

💡 Hint

Consider the position of the wildcard and the routing key words.

The binding key log.error.* matches routing keys starting with log.error. followed by exactly one word. Both log.error.system and log.error.application match this pattern.

❓ Troubleshoot

advanced

Why messages are not routed as expected

A queue is bound to a topic exchange with the binding key sensor.#. Messages with routing key sensor are not delivered to the queue. What is the most likely reason?

A The queue is not properly bound to the exchange

B The binding key 'sensor.#' only matches routing keys with exactly two words

C The routing key must have at least one word after 'sensor' to match 'sensor.#'

D The '#' wildcard does not match zero words, only one or more

💡 Hint

Check how the '#' wildcard behaves with zero words.

The binding key sensor.# matches routing keys starting with 'sensor' followed by zero or more words separated by dots. However, the routing key 'sensor' has only one word and no dot, so it does not match the pattern which expects 'sensor.' followed by words.

✅ Best Practice

expert

Optimizing topic exchange bindings for performance

Which practice helps improve performance when using topic exchanges with many bindings and high message throughput?

A Use fanout exchanges instead of topic exchanges for all routing needs

B Use more specific binding keys with fewer wildcards to reduce routing overhead

C Use only '#' wildcards in all bindings for maximum flexibility

D Bind all queues with the same binding key to simplify routing

💡 Hint

Think about how routing keys and bindings affect message routing speed.

More specific binding keys with fewer wildcards reduce the number of matches the exchange must check, improving routing performance. Overusing wildcards like '#' can cause more routing overhead.