AWS - Things to remember

DynamoDB
Query:

• DynamoDB supports the Query operation on table, a local secondary index, or a global secondary index that have a composite primary key (partition key and sort key). You can also filter query results.
• result set size limit of 1 MB
• Global secondary indexes support eventually consistent reads only

BatchGetItem:

• returns the attributes of one or more items from one or more tables
• can retrieve up to 16 MB of data, which can contain as many as 100 items

S3:

100 buckets per account (not region)

Bucket Naming convention:

• Bucket names must be at least 3 and no more than 63 characters long.
• Bucket names must be a series of one or more labels. Adjacent labels are separated by a single period (.). Bucket names can contain lowercase letters, numbers, and hyphens. Each label must start and end with a lowercase letter or a number.
• Bucket names must not be formatted as an IP address (e.g., 192.168.5.4).
• When using virtual hosted–style buckets with SSL, the SSL wildcard certificate only matches buckets that do not contain periods. To work around this, use HTTP or write your own certificate verification logic. We recommend that you do not use periods (".") in bucket names.
• No Upper case characters allowed

ELB:
Request Routing

Before a client sends a request to your load balancer, it resolves the load balancer's domain name using a Domain Name System (DNS) server. The DNS entry is controlled by Amazon, because your instances are in theamazonaws.com domain. The Amazon DNS servers return one or more IP addresses to the client. These are the IP addresses of the load balancer nodes for your load balancer. As traffic to your application changes over time, Elastic Load Balancing scales your load balancer and updates the DNS entry. Note that the DNS entry also specifies the time-to-live (TTL) as 60 seconds, which ensures that the IP addresses can be remapped quickly in response to changing traffic.

The client uses DNS round robin to determine which IP address to use to send the request to the load balancer. The load balancer node that receives the request uses a routing algorithm to select a healthy instance. It uses the round robin routing algorithm for TCP listeners, and the least outstanding requests routing algorithm (favors the instances with the fewest outstanding requests) for HTTP and HTTPS listeners.

The cross-zone load balancing setting also determines how the load balancer selects an instance. If cross-zone load balancing is disabled, the load balancer node selects the instance from the same Availability Zone that it is in. If cross-zone load balancing is enabled, the load balancer node selects the instance regardless of Availability Zone. The load balancer node routes the client request to the selected instance using its private IP address.

Ref: http://docs.aws.amazon.com/ElasticLoadBalancing/latest/DeveloperGuide/how-elb-works.html