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How to pick right database Depend on the question, read-heavy, write-heavy, or balanced workload? throughput needs? How much data to store and for how long? Will it grow? Data durability? Latency requirements? Strong schema or flexibility? It depends on a ...

Athena Query service that let you analyze data stored in S3. It uses SQL language to do the query. You will be putting data into S3 then you will query it with Athena. You pay per TB of data scanned. No need to pay for any server since it is serverless. It...

Rekognition A machine learning service to find object, people, text, scenes in images and videos. Facial analysis and facial search to do user verification works as well. You can use it to do labeling, content moderation, text detection, and many things. Co...

CloudWatch CloudWatch Metrics CloudWatch provides metrics (variable that you want to monitor) for every services in AWS. A metric belong to namespaces which is per services. 10 Dimension per metrics, associated instance id, environments, ...etc. You can ev...

Encryption 101 Encryption in flight: Achieved via SSL, your connection to the web server is encrypted, so no one can man in the middle you and sniff the packet that you're sending to find sensitive data SSL certificates is used to established the secure conn...

Organization Let you manage multiple AWS account at the same time. There is one main account that's the management account, other account are member accounts. Billing will all be sent to the management account. You get pricing benefits from using all service...

Networking 101 IP Addresses Every host or device on a network must be addressable, meaning that they should have something that can be referenced by in order to reach it as a destination under a defined system of addresses. That thing is called IP Addresses ...

Disaster recovery Disaster recovery is about preparing for those disaster that can happen to the data center. RPO: Recovery point objective. How often do you run backups. How far can you go back just before the data loss. "How much data did you lose just bef...

Event processing in AWS SQS + Lambda Lambda service is going to poll from SQS, however, there can be problem with the message if it cannot be processed and go into infinite loops. In that case a dead letter queue can be set up to sent problematic message aft...

CloudFormation Declarative way for outlining your AWS infrastructure using a template. "I want a security, I want two EC2 instance using security group" Then CloudFormation will create your instances, infrastructure as code, you will never create the resour...

If binary is relative to your current directory If the binary/script is relative to your current directory, then you would have to use ./ (dot slash) to execute the binary or script with respect to your current path. This is because your current directory is...

Did you ever wonder why when you run git checkout <branch name> from say a feature branch to the main branch it will fail? Well there could be many reason, the primary reason is that you have some local changes that you didn't commit / stash before switching t...

Branch name inconsistency Sometimes the branch name shown in git are inconsistent. For example, the output for git branch -a vs git branch -r. The remote-tracking branches will be prefixed with remotes/ in git branch -a. However, the remote branch in git bra...

https://howtodoinjava.com/maven/maven-parent-child-pom-example/

To remove all unwanted un-tracked files you can just run: git clean Use it with -n for a dry run to see the list of files that it will be removing. Use it with -d to also remove directories, can be used with -n.

Module? A module is just a Python file with the corresponding .py extension. So if you're talking about the math module then there is a corresponding math.py file that contains functions, classes, and constants that are meant to be used by other Python files....

Java Logging Logging in a program is important to keep track of a program's run-time behavior. Logs capture and persist the important data and make it available for analyst later on. Logging frameworks In Java there are multiple frameworks that you can use ...

System property value They are contained only within the Java platform. Environment variables are global at the operating system level. You can set system property value via CLI using -Dpropertyname=value You set environment variable using export envName=v...

In a application.properties file you can use place holders to reference environment variables rather than hard coding the value. For example: Instead of writing your application.properties like so: // application.properties aws.region=east Which is fine but...

The eval command can be used with either table data or event data.If used with event data the new field that is created won't be shown, because the event tab only shows the event data as a whole. Duh. To show the new field that you have created then you will ...