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DynamoDB Time-to-Live (TTL) is a mechanism that lets you set a specific timestamp to delete expired items from your tables. Once the timestamp expires, the corresponding item is marked as expired and is subsequently deleted from the table. TTL can help you reduce storage usage and reduce the cost of storing data that is no longer relevant.

Use cases

There are two main scenarios where TTL can come in handy:

1. Fine Grained Access Control (FGAC) gives a DynamoDB table owner a high degree of control over data in the table.

2. The table owner can indicate who (caller) can access which items or attributes of the table and perform what actions (read / write capability).

3. FGAC is used in concert with AWS IAM, which manages the security credentials and the associated permissions.

These are notes on some useful APIs to work with GSI and LSI.

Query API (GSI/LSI)

GSI support Query and Scan.

In addition to the common query parameters, a Query command explicitly includes the name of the index to operate against.

A query can use only one index.

A Query operation only searches index key attribute values and supports a subset of comparison operators.

1. an index with a partition or a partition-and-sort key that can be different from those on the table.

2. "global" because queries on the index can span all items in a table, across all partitions.

3. GSI behavior is similar to that of a DynamoDB table: You can query a GSI using its partition key element, with conditional filters on the GSI sort key element.

1. an index that has the same partition key as the table, but a different sort key. E.g. tracks Orders for customers, where CustomerId is the partition key.

2. "local" in the sense that every partition is scoped to a table partition that has the same partition key.

3. When you query a LSI, DynamoDB can access any of the projected attributes, with the same performance characteristics as if those attributes were in a table of their own.

VM Import/Export enables you to easily import virtual machine images from your existing environment to Amazon EC2 instances and export them back to your on-premises environment.

AWS Lambda is a higher level abstraction that lets you run code without provisioning or managing servers, following the servlerless architecture. You can run code for virtually any type of application or backend service with no administration.

You just needs to upload your code and Lambda takes care of everything required to run and scale your code with high availability, such as server and operating system maintenance, capacity provisioning, automatic scaling, code and security patch deployment, code monitoring and even logging.

Auto Scaling helps you maintain application availability and allows you to dynamically scale your Amazon EC2 capacity up or down automatically according to conditions you define.

You can use Auto Scaling for Fleet Management of EC2 instances to help maintain the health and availability of your fleet and ensure that you are running your desired number of Amazon EC2 instances.

Secure Sockets Layer/Transport Layer Security (SSL/TLS) certificates are used to secure network communications and establish the identity of websites over the Internet.

AWS Certificate Manager is a service that lets you easily provision, manage, and deploy SSL/TLS certificates for use with AWS services.

AWS Certificate Manager removes the time-consuming manual process of purchasing, uploading, and renewing SSL/TLS certificates.

A load balancer is a device that acts as a reverse proxy and distributes network or application traffic across a number of servers. Load balancers are used to increase capacity (concurrent users) and reliability of applications. 

Amazon Elastic Load Balancing (ELB) automatically distributes incoming application traffic across multiple EC2 instances. ELB also automatically scales its request handling capacity to meet the demands of application traffic.