Services - Application Integration

Question 1

SNS - Characteristics

Answer 1

• It’s a managed service that provides message delivery from publishers to subscribers, by sending messages to a topic
• Message durability is achieved by having a delivery retry policy (for each delivery protocol), and by allowing the creation of dead-letter queues to preserve messages
• Pay for what you use, based on the type of topic used

Question 2

SNS - Ways of communication

Answer 2

• Application to application messaging from a publisher to an AWS service, HTTP / HTTPS, and others
• Application to person notifications from a publisher to mobile applications, mobile phone numbers, and email addresses

Question 3

SNS - Topic types

Answer 3

• Standard: when message delivery order and possible message duplication are not critical
• FIFO: to ensure strict message ordering, define message groups, and prevent message duplication

Question 4

SNS - Creation steps

Answer 4

1. Create a topic
2. Define a topic policy. Where you define: which users can publish to it, which users can subscribe to it, and the delivery protocols allowed
3. Create a subscription by defining topic, protocol, and the endpoint
4. Create and define the publisher, like a S3 bucket

Question 5

SQS - Characteristics 1

Answer 5

• It offers a secure, durable, and available hosted queue. A message can be up to 256KB
• Amazon MQ is a message broker and is recommended for migrating applications from other message brokers
• To provide prioritization of work AWS recommends to use separate queues. An custom application will be responsible for prioritization
• Pay for what you use. The number of requests, data transferred in / out, and integration with other services are charged

Question 6

SQS - Characteristics 2

Answer 6

• Default visibility timeout: time available to read the message using AWS CLI or AWS console. The message can be read multiple times
• Delay Queue is a queue that allows to delay the delivery of messages to a queue for up to 15 minutes
• Dead-Letter Queue is a queue for those messages that are not consumed successfully. It’s used to handle message failure

Question 7

SQS - Queue types

Answer 7

• Standard:
• The message order isn’t preserved. Messages can be consumed twice or multiple times
• Processes an unlimited number of transactions per second
• FIFO:
• The message order is preserved. Messages get consumed only once
• Processes up to 300 messages per second

Question 8

SQS - Short and long polling

Answer 8

• By default, queues use short polling
• With short polling, a ReceiveMessage request queries only a subset of the servers to find messages available to include in the response. SQS sends the response, even if the query found no messages. Subsequent requests will return the rest of messages
• Receive Message Wait Time: maximum amount of time that SQS waits for messages to become available after the queue gets a receive request
• When “Receive Message Wait Time” is greater than 0, long polling is in effect
• With long polling, a ReceiveMessage request queries all of the servers for messages. SQS sends a response with at least one available message or up to a specified maximum number of messages. SQS sends an empty response only if the polling wait time expires.