System Design | Implementation Rule Book | CheatSheet

    Annotations are useful to tell: -Constraints or usage of an element: e.g. @Deprecated, @Override, or @NotNull - The "nature" o...

 There are various ways , the application can notify a set of recipients based on the error catrgories.  Spring email: configure logback xml...

 Spring retry is one of the implementation in Retryable Programming. Code snippet: Foo foo = template.execute(new RetryCallback<Foo>()...

 An application must be set with enough memory to be able to function as per the SLA. It should not be under or over utilised. Things to be ...

Redirect stderror to output $ cat foo.txt > output.txt 2>&1  // 2 stderror, &1 std output cat nopx.txt > outputx.txt 2>...

 #How to find process id of a running program on a given port sudo lsof   -i:8080 sudo lsof   -i:443

Secure shell:  Connect Remote server using SSH protocol -check existing key :ls -al ~/.ssh // It shows existing public and private key pair...

Real: wall clock time – time from start to finish of the call. User: the amount of CPU time spent in user-mode code (outside the kernel) w...

Steps to do rolling restart of ES cluster: sudo su root docker ps -a docker stop/start <I_ID> docker exec -it <IMG_Id> /bin/bash...

1.  Stream to Map Map<Integer, String> result3 = list.stream().collect( Collectors.toMap(x -> x.getId(), x -> x....

Creational Structural Behavioural Abstract Factory Assember Accumumator ...

Dynamically create your own BeanDefinition BeanDefinitionRegistryPostProcessor has a hook on the BeanDefinitionRegistry @Component public cl...

About Terraform: A declarative language,  not a programming language. Which keeps its state recorded when we run again it compares the new a...

This blog covers the basics of terraform a declarative language for managing infrastructure as code.  Download link:  brew install terraform...

VPC: Egress-only internet gateways: - allows outbound communication over IPv6 from instances in your VPC to the internet, and preven...