Concepts
Synchronous communication implies a real-time interaction between the sender and the receiver. The sender sends a request and waits for the response before continuing with further processing. This pattern is often seen in request-response models.
Characteristics
- Blocking: The sender is blocked until the response is received.
- Immediate Feedback: Provides instant acknowledgment about the success or failure of the operation.
- Simplicity: Easier to understand and implement because of its linear nature.
- Latency-Sensitive: The time taken for the round trip of a request-response impacts the performance.
Examples in AWS
- Amazon EC2: When you make a request to launch instances, you receive an immediate response indicating whether the request was successful.
- AWS Lambda: Invoking Lambda functions synchronously, using the
InvokeAPI with theRequestResponseparameter, will wait for the function to process the event and return a response. - Amazon RDS: When sending SQL queries to RDS, you expect immediate results from the database.
Code Sample
When invoking a Lambda function synchronously:
import boto3
lambda_client = boto3.client(‘lambda’)
response = lambda_client.invoke(
FunctionName=’MyLambdaFunction’,
InvocationType=’RequestResponse’,
Payload=b'{“key”: “value”}’
)
print(response[‘Payload’].read())
In the above code, InvocationType='RequestResponse' indicates a synchronous execution where the client waits for the AWS Lambda function to complete and return a response.
Asynchronous Communication
In contrast, asynchronous communication does not require the sender to wait for the immediate response. The sender can continue with other work, and processing of the message is handled independently by the receiver.
Characteristics
- Non-Blocking: The sender sends a message and continues without waiting for a response.
- Delayed Feedback: Confirmation of the message receipt or processing success may not be immediate.
- Scalability: Better suited for scaling as it allows the receiver to handle messages at its own pace.
- Complexity: Can be more complex to implement because it may require additional handling for message delivery, processing, and error management.
Examples in AWS
- Amazon SNS: Messages are published to a topic and then processed by subscribers independently.
- AWS Lambda: Invoking Lambda functions asynchronously using the
Eventinvocation type; the function invocation returns immediately. - Amazon SQS: Messages are pushed to SQS and are processed later by consumers polling the messages.
Code Sample
When invoking a Lambda function asynchronously:
import boto3
lambda_client = boto3.client(‘lambda’)
response = lambda_client.invoke(
FunctionName=’MyLambdaFunction’,
InvocationType=’Event’,
Payload=b'{“key”: “value”}’
)
# The response will only contain the status code and request ID, not the function’s output
In the above example, InvocationType='Event' indicates an asynchronous execution where the Lambda function is invoked, and the caller can immediately proceed without waiting for the function to process the event.
Comparison Table
| Aspect | Synchronous | Asynchronous |
|---|---|---|
| Communication Mode | Request and Response | Fire and Forget |
| Sender Behavior | Waits for response | Continues processing |
| Latency | Depends on round trip | Not immediately relevant |
| Use Cases | Real-time processing, Web services | Distributed systems, Event-driven architectures |
| AWS Services | EC2, RDS, API calls with “RequestResponse” | S3 event notifications, SNS, SQS, Lambda with “Event” |
Understanding when to use synchronous versus asynchronous communication can profoundly impact the design of your applications. Synchronous patterns are suitable when immediate processing and responses are necessary, while asynchronous patterns are best when the work can be processed at a later time or requires decoupling for scalability and fault tolerance. Deciding between the two will often come down to the specific requirements of the application or system you are developing and deploying on AWS.
Answer the Questions in Comment Section
True or False: Synchronous communication requires the client to wait for the server to respond before proceeding with other tasks.
- Answer: True
In synchronous communication, the client sends a request and waits for the response from the server before it can continue with other work.
True or False: Asynchronous communication patterns can help achieve higher levels of scalability in distributed systems.
- Answer: True
Asynchronous communication allows multiple requests to be handled independently, thus can improve scalability by not holding up resources.
In asynchronous communication, does the client typically receive an immediate confirmation that a request has been received before the actual processing starts?
- A) Yes, always
- B) Only for certain services
- C) No, never
Answer: B) Only for certain services
In some asynchronous systems, the client might receive an acknowledgment that a request has been queued, but it’s not always an immediate confirmation of receipt.
Which AWS service provides a managed asynchronous message queue?
- A) AWS Lambda
- B) Amazon SNS
- C) Amazon SQS
- D) Amazon EC2
Answer: C) Amazon SQS
Amazon SQS (Simple Queue Service) provides a managed message queue for asynchronous processing.
True or False: AWS Lambda can only be invoked synchronously.
- Answer: False
AWS Lambda functions can be invoked either synchronously or asynchronously, depending on the configuration and event source.
Which of the following is a characteristic of synchronous communication?
- A) Decoupling of service providers and consumers
- B) Immediate response requirement
- C) Inherent scalability
- D) Delay tolerance
Answer: B) Immediate response requirement
Synchronous communication is characterized by the requirement for an immediate response.
Multiple select: Which AWS services naturally support asynchronous processing? (Select two)
- A) Amazon API Gateway
- B) AWS Step Functions
- C) Amazon Simple Notification Service (SNS)
- D) Amazon Simple Queue Service (SQS)
Answer: C) Amazon Simple Notification Service (SNS), D) Amazon Simple Queue Service (SQS)
Both Amazon SNS and SQS support asynchronous processing by allowing messages to be published and consumed at different rates.
True or False: An AWS Lambda function triggered by an S3 event can process files synchronously as they are uploaded to the bucket.
- Answer: False
When AWS Lambda is triggered by an S3 event, it processes the event asynchronously after the file has been uploaded.
How does error handling typically differ between synchronous and asynchronous patterns?
- A) There is no difference in error handling.
- B) Synchronous patterns return errors directly to the client, while asynchronous patterns require error handling mechanisms such as dead letter queues.
- C) Asynchronous patterns allow retries without client intervention, while synchronous patterns often require manual retries.
- D) Synchronous patterns use queues for error handling, while asynchronous patterns do not.
Answer: B) Synchronous patterns return errors directly to the client, while asynchronous patterns require error handling mechanisms such as dead letter queues.
In synchronous patterns, errors are returned immediately to the client, whereas asynchronous systems often use mechanisms like dead letter queues to handle message processing failures.
Which AWS service is best suited for synchronous serverless computing where the client needs an immediate response?
- A) AWS Lambda
- B) Amazon EC2
- C) Amazon S3
- D) Amazon RDS
Answer: A) AWS Lambda
AWS Lambda can be used for synchronous serverless computing by providing immediate responses to triggering events when configured to do so.
True or False: AWS SNS supports both synchronous and asynchronous message delivery.
- Answer: False
AWS SNS is designed primarily for asynchronous message delivery, to decouple the sending and receiving of messages.
In a synchronous pattern, if a web service goes down temporarily, what typically happens to client requests?
- A) They are automatically retried until the service is back up.
- B) They are queued until the service can handle them.
- C) They fail and the client receives an error response.
- D) They are redirected to a backup service.
Answer: C) They fail and the client receives an error response.
In synchronous communication, if the server is down, the client’s requests will fail, and the client typically receives an error message indicating the failure.
Can someone explain how promise-based async calls work in Lambda functions?
Great breakdown on sync vs async patterns! Really helpful for the AWS DVA-C02 exam.
Thanks for the insights! This will definitely help me prepare for the exam.
The difference between sync and async was always confusing to me, but this blog cleared it up.
I think synchronous patterns can sometimes lead to performance bottlenecks in high-load systems. Thoughts?
Why would you ever use synchronous calls in a cloud environment?
Good article, but it could have used more detailed examples.
This blog post is a life saver for AWS certification prep!