Applications Flashcards
What is SQS
It a messaging system, where message could be saved by s3 or ec2 instances, which could then be processed by other compute services.Messages are 256 kb in size and go up t 2gb, but S3 is needed for that. Messages are retained for 4 days by default and it could be varied from 1 min to 1 year
What are the types of SQS?
General or Standard queue: where the messages are generally in the order they are received, There could be duplicates and ordering is also not guaranteed.
FIFO queue: Messages are in the saved in a FIFO way
There are no duplicates. limited to 300 transaction per second
What is visibility timeout in sqs?
When EC2 picks up a message for processing from SQS, the message disappears for others to process. If EC2 doesn’t clear the message within a timeout period, the message will appear again. The max visibility period is 12 hours
What is SWF?
Used when we need to integrate some kind of Human interaction with code based actions.It has workflow starters, deciders and activity workers.
Difference between SWF and SQS
SWF workflows can run for 1 year, whereas SQS has a retention period of 14 days.
What is SNS?
Push based service used to send message to different devices by text or notifications.Its inexpensive and no upfront costs.
What is Elastic Transcoder?
It is a media transcoder, converting media from one format to other.We can upload video to S3, which can trigger a transcoder to convert it from one format to other, which can play in mobile and other devices
Benfits of API Gateway
Can be used to cache data to improve performance.
it is low cost and scales automatically
can log results to cloudwatch.
What is kinesis?
it’s a service to store large volumes of small sized streaming data. Data inside kinesis is stored in shards.The data itself is stored for 24 hours by default and can be extended to 7 days. Stored data can be analysed by other ec2 instances, and saved to databases or whatever seems fit.
what is kinesis Firehose?
It is a kind of kinesis where the incoming data is not stored, but rather a lambda function or some kind of trigger is initiated to act upon the data.
What is kinesis analytics?
A service used to anlayse the incoming streaming data in
Kinesis streams or Kinesis firehose
What are the types of Kinesis
Kinesis Firehose and kinesis stream.
Is SQS General queue compatbitle with FIFO queue?
Not all services might be compatible
How is SQS charged?
It has free tier and beyond which a charge will incure base on number of messages. Requests could be batched to get cost benefits.
What is long and short polling?
Short polling returns immediately even if the queue is empty, where as long polling wait for some message to arrive before returning to client or time out to happen.
Long polling is cost effective, but it can block teh calling thread, till reposne is received.
