SNS - Simple Notification Service
Highly available, durable secure fully managed pub/sub messaging service.
Has Topics and subscriptions
Supports destination for both application and human(text, email, pager, etc…)
Types of topics: Standard, FIFO(first in first out, guarantees order).
Messages: Standard messages upto 256kb, can support up to 2gb if use the extended library which uses s3 as a middleware
Subscriptions: can only describe one protocol and one topic. Http, HTTps, Email, sqs, lambda, sms, application endpoint.
Filter Policy: filter a subset of messages so that only the filtered ones get delivered.
Scope: messageAttributes, MessageBody Options: AND, OR logics, key matching, number matching
There is also data protection, to audit, mask, redact, or block sensitive information.
Delivery Policy: defines how SNS retries the delivery of messages when server-side errors occur. Each delivery protocol has its own delivery policy.
If the retry limit is reached, it stops and discards the message unless there is a dead-letter queue.
Dead-leater queue - DLQ sends failed messages there. which is a SQS queue