No	Q	A	Ref
1	ELB - User login randomly	ELB Sticky Session + Store session in DynamoDB
2	Config SQS Short/Long Polling	Queue’s ReceiveMessageWaitTimeSeconds attribute ReceiveMessage call’s WaitTimeSeconds param
3	DynamoDB TTL	1 process using TTL attribute and mark expired another process delete these expired items
	DynamoDB Streams	DynamoDB Stream is a 24h flow of item changes
4	Lambda function reuse execution environment between invocations	Cache static assets locally in the /tmp directory	Lambda Best Practice
		Initialize SDK clients and database connections outside of the function handler
5	Best practice to apply permissions to an EC2 instance	EC2 Instance Profile
6	Serve private content with CloudFront & S3	- Require users access private content by using CloudFront signed URL, signed cookies:	Serve Private Content
		👈️ This is implicit enabled after a signer is added
		- Require users access your content by using CloudFront URLs, not directly from origin:
		👈️ This is done with OAC (for S3 origin), or custom header (for custom origin)
7	Protect API Gateway & Lambda	Both run outside VPC, needs to use WAF
8	S3 - Encryption in transit	It’s default
9	Process orders in 48 hours (in the origin order) & Cost effective	48 hours -> Not Lambda -> Step Function + Lambda
		In order -> SQS FIFO
10	Using CWAgent to write logs to CloudWatch Logs from an EC2 instance in private subnet	- CloudWatch Logs is an public service, which can be access other AWS services, or on-premise servers.
		- To send logs to CloudWatch Logs without sending them through the internet,
		1. A private connection needs to be established between your VPC and CloudWatch Logs	Using CloudWatch Logs with interface VPC endpoints
		2. The EC2 instance have enough permissions to send logs to CW Logs
		2a. EC2 instance profile (role) have permissions	Grant permissions that the CloudWatch agent needs to write metrics to CloudWatch
		2b. Endpoint allows access (by default, endpoint policy allow all access to it)	Default endpoint policy
11	API - Gateway - Use the same function for multiple stages?	Use stage variable to change the endpoint for each stage	API Gateway - Stage variable
12	How to give custom permissions to millions of users?	Use Cognito Federated Users + IAM policy variable	IAM Policy for federated users
13	RDS Replica endpoints	Each RDS Replica has its own endpoint. Except Aurora, RDS doesn’t provide a reader endpoint with load balancing
14	Add sign up, sign in features	Cognito User Pool
15	DynamoDB RCU/WRU calculation	1 RCU = 4KB/s, 1 WRU = 1KB/s
16	Where to store CW Agent config?	SSM Parameter Store
17	Elastic Beanstalk deploy to brand new infrastructure	- EB immutable deployment	Elastic Beanstalk & Blue-Green deployment
		- Manually deploy to a new environment, EB supports swap DNS to the new environment
18	API Gateway - Legacy APIs required transformation	Use integration HTTP
19	Delete all items in a DynamoDB table everyday?	??? Use DynamoDB TTL
20	Route traffic from ELB to Lambda functions	You can register your Lambda functions as targets of ELB listener
21	SQS message size limit	256KB. To work with larger files, offload it to S3
22	CloudFormation: Share stack vs share template	Share stacks with Stack Reference; Share template with Nested Stack
23	Where is CORS applied?	CORS is applied to the origin being accessed, not the origin accessing.
24	Which services use CloudFormation under the hood?	SAM, Elastic Beanstalk
25	What is the size limit for data sent to AWS KMS?	4KB. To encrypt larger file, use DEK and envelope encryption
26	S3 encryption by S3 server, manage key by application	SSE-C
27	???
28	Tracing between many AWS services	X-ray
29	Host website on S3	- Turn on Static Website Hosting
		- Allow public access with bucket policy
30	Decouple apps & Serverless scaling	Use SQS + Lambda (config function concurrency)
31	Give access to CodeCommit repo	CodeCommit control access via IAM users: Create HTTPs credential in IAM; or create SSH key & associate to IAM user
32	Whenever a new comment added, send an email?	DynamoDB Stream + Lambda trigger + SNS
33	SQS: Messages process twice?	VisibilityTimeout not long enough
34	Import APIs to API Gateway	Import OpenAPI definitions
35	Upload file to S3 - Improve performance?	Transfer Acceleration
36	Kinesis: Improve performance?	Increase number of shards (shard splitting)
37	Lambda: Share library	Lambda Layer
38	Collect real time data	Kinesis Data Streams
39	Reuse Lambda function for multi stages	Use stage variable
40	Embed Lambda function in CloudFormation template	Code’s ZipFile
41	Host static website	S3 + CloudFront
42	Config/Update EC2 instance with CloudFormation	cfn-init + cfn-signal & cfn-hup
43	Query only a part of data on S3	S3 Select
44	Attach an EBS volume to EC2 instance	Create file system; Mount it
45	DynamoDB: Primary key	Student ID
46	APIs to request temporary credentials with IAM	AssumeRole, AssumeRoleWithSAML, AssumeRoleWithWebIdentity
47	API Gateway: Ensure searchString parameter is in the request	Method Request
48	Increase CPU allocation of a Lambda function	Increase memory allocation
49	CloudWatch namespace & metrics
50	Run AWS CLI in EC2, what will happened?	It won’t run. AWS CLI use other credential first ???
51	DynamoDB WCU	Write operation is not strongly/eventually consistent. Only read has consistent problem.
52	Send a message to user	SNS
53	S3 ListAPI	max-items, page-size
54	DynamoDB: Improve read performance	DAX
55	Migrate microservice to AWS, low operation overhead	ECS Fargate
56	DynamoDB eventually read	Use less RCU than strong consistent read, may receive outdated data
57	Which S3 encryption option can be used with CloudHSM?	CSE
58	CloudFront stale object	Invalidate
59	Failover to an maintenance page on S3	Route 53 + Health-check
60	S3: Block all access except from CloudFront	OAC, OAI (legacy)
61	Improve performance of app (using DynamoDB) without modify code	Increase RCU
62	Application workflow take up to 45 min + Cost effective	Step Function + Lambda
63	ASG: Instances started & terminated rapidly	Increase cooldown time
64	SQS + 5 EC2 instances	Increase polling time; Use ASG for scaling based on queue length
65	Check if a Spot instance is terminated	Use instance metadata service