Synchronous vs asynchronous communication in Microservices - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to show a synchronous call between services.

Microservices

response = serviceA.call_serviceB([1])

Drag options to blanks, or click blank then click option'

Await_for_response

Bfire_and_forget

Csend_request_and_wait

Dpublish_event

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing 'fire_and_forget' which is asynchronous behavior.

In synchronous communication, the caller sends a request and waits for the response before continuing.

2fill in blank

medium

Complete the code to send an asynchronous message.

Microservices

message_queue.[1](event)

Drag options to blanks, or click blank then click option'

Apublish_event

Bsend_request_and_wait

Ccall_service

Dwait_for_response

Attempts:

3 left

💡 Hint

Common Mistakes

Using synchronous call methods instead of event publishing.

Publishing an event to a message queue is an asynchronous way to communicate between services.

3fill in blank

hard

Fix the error in the synchronous call to avoid blocking indefinitely.

Microservices

response = serviceA.call_serviceB(timeout=[1])

Drag options to blanks, or click blank then click option'

A-1

B0

CNone

D30

Attempts:

3 left

💡 Hint

Common Mistakes

Using None or zero which may cause indefinite blocking.

Setting a timeout (e.g., 30 seconds) prevents the caller from blocking forever if the service does not respond.

4fill in blank

hard

Fill both blanks to create an asynchronous event handler that processes messages.

Microservices

def handle_event(event):
    [1] = event.get('data')
    process([2])

Drag options to blanks, or click blank then click option'

Adata

Bevent_data

Devent

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names causing undefined errors.

The handler extracts 'data' from the event and processes it asynchronously.

5fill in blank

hard

Fill all three blanks to implement a retry mechanism for synchronous calls.

Microservices

for attempt in range([1]):
    try:
        response = service.call()
        if response.status == [2]:
            break
    except [3]:
        continue

Drag options to blanks, or click blank then click option'

A3

B200

CTimeoutError

D5

Attempts:

3 left

💡 Hint

Common Mistakes

Using too many retries or wrong exception types.

Retry up to 3 times, break if HTTP 200 OK received, and catch timeout errors to retry.

Practice

1. Which statement best describes synchronous communication in microservices?

easy

A. The caller waits for the response before continuing.

B. The caller sends a request and continues without waiting.

C. The services communicate only through message queues.

D. The services never exchange data directly.

Solution

1. Step 1: Understand synchronous communication

   Synchronous communication means the caller waits for the response before moving on.

2. Step 2: Compare options

   The caller waits for the response before continuing. matches this definition exactly, while others describe asynchronous or unrelated concepts.

3. Final Answer:

   The caller waits for the response before continuing. -> Option A

4. Quick Check:

   Synchronous = Wait for reply [OK]

Hint: Synchronous means wait for reply before next step [OK]

Common Mistakes:

• Confusing synchronous with asynchronous communication
• Thinking synchronous means no waiting
• Assuming message queues are always synchronous

2. Which of the following is the correct way to describe asynchronous communication in microservices?

easy

A. The caller blocks until the response is received.

B. The caller uses a direct function call to get the result.

C. The services must be on the same server.

D. The caller sends a request and processes the response later.

Solution

1. Step 1: Define asynchronous communication

   Asynchronous means the caller sends a request and does not wait; it handles the response later.

2. Step 2: Evaluate options

   The caller sends a request and processes the response later. correctly describes this behavior. Options A and D describe synchronous calls, and C is unrelated.

3. Final Answer:

   The caller sends a request and processes the response later. -> Option D

4. Quick Check:

   Asynchronous = Send and continue [OK]

Hint: Async means send request, handle reply later [OK]

Common Mistakes:

• Mixing up blocking and non-blocking calls
• Assuming async requires same server
• Thinking async means no response

3. Consider this pseudocode for a microservice call:

response = callServiceSync(request)
print("Done")

What will be the output order?

medium

A. "Done" prints before the service responds.

B. "Done" prints after the service responds.

C. The code throws an error because of missing callback.

D. The code runs asynchronously without waiting.

Solution

1. Step 1: Analyze synchronous call behavior

   The function callServiceSync waits for the service response before returning.

2. Step 2: Determine print timing

   Since the call blocks, "Done" prints only after the response is received.

3. Final Answer:

   "Done" prints after the service responds. -> Option B

4. Quick Check:

   Synchronous call blocks, then prints [OK]

Hint: Sync calls block; print happens after response [OK]

Common Mistakes:

• Assuming print runs before response
• Confusing sync with async calls
• Expecting errors due to missing async syntax

4. A developer wrote this asynchronous call:

sendRequestAsync(request)
print("Request sent")
waitForResponse()

But the system blocks until the response arrives. What is the likely mistake?

medium

A. print statement should be after waitForResponse().

B. sendRequestAsync() is actually synchronous.

C. Calling waitForResponse() immediately blocks the flow.

D. The request object is malformed.

Solution

1. Step 1: Understand asynchronous call flow

   sendRequestAsync should not block, but waitForResponse() forces waiting.

2. Step 2: Identify blocking cause

   Calling waitForResponse() immediately after sends blocks the flow, negating async benefits.

3. Final Answer:

   Calling waitForResponse() immediately blocks the flow. -> Option C

4. Quick Check:

   Immediate wait blocks async [OK]

Hint: Waiting right after async call blocks it [OK]

Common Mistakes:

• Assuming async call is sync
• Misplacing print statement
• Blaming request format instead of flow

5. You design a microservice system where user requests must get immediate confirmation, but heavy processing can be delayed. Which communication pattern fits best?

hard

A. Use synchronous communication for confirmation and asynchronous for processing.

B. Use only synchronous communication for all tasks.

C. Use only asynchronous communication for all tasks.

D. Use synchronous communication for processing and asynchronous for confirmation.

Solution

1. Step 1: Analyze requirements

   Immediate confirmation requires waiting for a quick response (synchronous).

2. Step 2: Handle heavy processing

   Heavy tasks can be done later without blocking user, so asynchronous fits.

3. Step 3: Match communication patterns

   Combining synchronous for confirmation and asynchronous for processing meets both needs efficiently.

4. Final Answer:

   Use synchronous communication for confirmation and asynchronous for processing. -> Option A

5. Quick Check:

   Immediate reply = sync, heavy work = async [OK]

Hint: Immediate reply sync, heavy work async combo [OK]

Common Mistakes:

• Using only sync causes delays
• Using only async delays confirmation
• Reversing sync and async roles