Preparing for AWS Certified Developer

I have briefly mentioned about how I prepared for the other AWS certifications – Solution Architect and SysOps Administrator in other posts. I cleared my AWS Developer certification last week. It was indeed developer focused, which translates to heavy coverage of DynamoDB, CloudFormation, ElasticBeanstalk, SQS, SNS, Opsworks. DynamoDB stood out without any doubt.


Few interesting points – there were questions on command line, knowledge on hard limits and soft limits in AWS services, emphasis on usage of SDK (SDK user would be able to answer that question without a doubt). I am a developer not inclined to any particular platform but a more of a generic guy with bit of js, .net and python.

I have been working on AWS (and other random stuff – Azure, Office 365, Talend, Robotic Process Automation, devops) for around 6 years and I never really took a learning path to for AWS certification – associate level. I took my AWS Solution Architect by mid 2014, SysOps by mid 2015, solution architect recertification by mid of 2016 and developer certificate couple last week (end of 2016) (working on my professional level).

I would recommend the following learning path for someone who would want to face the AWS Certified Developer certification.

  1. VPC, Subnets, Security Groups, Elastic IP, Public IP, Private IP – have this by heart by all means. (although this is pretty much applicable for all the AWS certifications)
  2. EC2, AMI – try launching & relaunching in different AZ, different region, change size, change application version, snapshots – attach & detach
  3. S3 is really important – method of securing S3 items (ACL, IAM) – static web site, logging, storage classes and GLACIER [ I want to thank Craig Carl for his re:Invent session – please spend time in this video you would also thank Craig Carl when you face the certification)
  4. I would recommend ditching AWS management console for couple of weeks and using with AWS CLI and that should level up your skills in IAM Access Key – Secret Key, and understand the AWS API nature. Bonus points is when you try aws-shell.
  5. I remember watching one of the youtube videos by Matt Wood himself where he starts all the way from 101 in DynamoDB. I would recommend trying to build a web application using one of the SDKs with DynamoDB as backend + some CRUD application should help you get your hands dirty in DynamoDB. Please spend time, effort, money, social life on indexes in dynamodb.
  6. Try releasing the above application to the wide through OpsWorks and Beanstalk that would be help check lot of items in the exam blue print
  7. Try using RDS, SNS, SQS wherever and however possible
  8. If you are able to meaningfully represent the above stated items over a CloudFormation you are good to go here. I am bragging this.
  9. FAQs are super important for the services – I would do this multiple time before facing the certification exam
  10.  All the patterns and anti-patterns (When do you CloudFormation vs Elastic BeanStalk, AMI vs user data, RDS vs DynamoDB) would help filter the wrong answers. I felt this was a theme the whole time.

All the best

Sleep function in AWS CloudFormation

IMHO one of the most important missing pieces in CloudFormation is not having the ability to explicitly specify a SLEEP or WAIT function. It is not that it is totally impossible to the implement the same, except that, it would involve having a hard work around one of which is to inject the wait script via the user data with WaitHandle and WaitConditions on EC2 instances.

A sample implementation of wait using EC2 Instance’s WaitHandle

There is absolutely no downside to the approach and also it is easier to bake the wait script inside the CloudFormation template; the problem would arise if you wanted to have the same WAIT functionality to be implemented for the stacks which do not have EC2 instances as part of the stack.

I tried and succeeded using Amazon Lambda for the purpose instead of EC2. To summarize the implementation; a CloudFormation custom resource would call a lambda function and all that the function would do is to respond after 5 minutes [current maximum execution time for lambda function execution time]. Again, if you need to wait longer than 5 minutes, you would use the DependsOn in CloudFormation and cascade the Custom Resource Calling.

Wait Function – AWS Lambda

Below is the sample Code where you create a VPC and a Security Group after waiting a 5 minute delay time and 10 minute delay.




Preparing for Recertification – AWS Certified Solution Architect – Associate

I took and successfully cleared the Recertification exam for AWS Certified Solution Architect – Associate Level today. I am still regretting not attemting advancing to the professional level; anyway … here is the blog post about the recertification exam. I previously blogged about the Preparing for the AWS Certified Solution Architect – Associate level, 2 years ago.

I felt a couple of questions having been repeated from the original Solution Architect exam which I wrote 2 years back; I completely understand and agree the importance & reason why those were repeated again (I abide by the NDA signed hence not disclosing which questions – they are).

  • It was a quick 80 mins and 60 questions test
  • VPC, IAM, EC2, S3 – the core services are still important and had lot of depth and count
  • Following the same Learning Strategy for the original exam would still be relevant
  • Amazon did a good job of drawing a line to determine what are the points and factors (costing, sizing, strategy, design, optimal solution) which would affect or effect an Architect
  • If you are continuing your day to day AWS operations after you have Cleared your original AWS Certified Solution Architect – Associate Level, you be able to win hands down

I highly recommend giving it thought about NOT taking the recertification exam – Associate Level, and consider Professional Level, on clearing; you would be able to renew both the levels for next 2 years. I received a 50% voucher code almost a year back, I am sure you would have received one too for taking Professional Level (50% discount of $300).
PS : You get a new AWS-ASA XXX number instead of the same number renewed for next 2 years. It is good to know that lot of people are taking the certification exam – 2 years ago my certification number was in 2000s and now it is 20,000s; in short it is almost like a brand new exam but a discounted rate of $75 instead of $150.

Categories AWS

AWS CloudFormer for Non Default VPC

AWS CloudFormer helps you to create a CloudFormation template fcfnrom the AWS resources currently running in your account using a few simple steps. The current CloudFormer makes use of the Default VPC to get started; this is usually fine except for the scenarios where we have deleted the Default VPC. This is CloudFormer template forked from AWS provided to extend the capability to provide the ability to specify the VPC.

View in GitHub

If I were to write AWS CloudFormation template

This is a post where I would like to share about the things which I picked up over the course of time which has come really enjoyable writing an AWS CloudFormation template.

1. Editor : Sublime Text Editor with Neon Theme

I use Sublime Text Editor with Neon Theme to save time and not going mad over the missing { or } during the development phase. Sublime editor highlights the closing or opening of the braces which aids not having to run the counting of [Push & Pop] Compliers’ Stack program for the braces. It is not that other IDEs like Visual Studio or Eclipse or PyCharm are not useful; well actually they all have in fact inbuilt plugins with CloudFormation to deploy directly; but Sublime is light weight and simple. The intellisense like code suggestion in Sublime would really help not having to ignore the long naming styling for easy readability; example : ADInstanceEIP, ADInstanceEIPAttachment wouldn’t be a problem as the Sublime editor would automatically prompt that for you.

Untitled picture

To summarize, Sublime editor helps highlighting Opening and Closing { } and has a very good code suggestion and nice color.

2. Use the File format as JSON

The .json file extension for the CloudFormation template just works fine and we don’t have a hard and fast rule to use the .template all the time. Actually using the .json activates the IDEs to treat the code base with intelligence, syntax coloring and code suggestion prompts.

3. Prefer Mappings over Parameters

When I started writing the CloudFormation template, I used Parameters where ever possible and when ever possible; there by having the possibility of dynamism in the CloudFormation template. Essentially, that may not be true all the cases. It was more like a thumb-rule to use AMI mappings in MAPPINGS block and rest of them in Parameters.


When I realized there was a very very handful number of times, I actually had used the parameters. When I moved the entities from Parameters to Mappings; I actually started building the Class like structure for the entire stack. It is not hard coding at the same time easy to have all the things that would change in exactly one place and aid rapid copy pasting functionality.


3. Region Mapping with AZ Dropdown

All the sample templates from CloudFomation library has the region mapping; so template becomes region independent with no additional effort except that you need to ensure the AMI are created (or copied) to the designated regions and those AMIs are placed in Mappings block.


I use the AWS::EC2::AvailabilityZone::Name which is extremely handy during my AWS DR Scenario or DR-like Scenario or DR Drills [ Yes I just coined the term DR-like Scenario🙂 ] where it prompts the available AZ.

4. Splitting CloudFormation Templates – Networks Separately, Instance Separately [Nested Stack]

Nested Stacks would be in the must use case where the environment involves several Route Table Routes and/or ACL rules as every single rule is resource in the terminology of the CloudFormation where it is currently maxed at 200 resources. The solution is to separate the Route Table rules in a separated nested template and ACL rules in a different one.

5 . A Resource can wait for dependency of completion after multiple other Resources

There are few cases where you might need to wait for multiple resources to be completed before initiating the new resources creation; this is not required most of the time but during the demo :).

Also the DependsOn doesn’t require usage of Ref i.e. DependsOn : {Ref : “Resource”} but DependsOn : “Resource” or  DependsOn : [“Resource”]


6. Don’t use IDE’s Default format code

I prefer to not use any of the IDE’s default formatting options as IMHO make the code look long if there is anything it make the JSON / JS code look lengthier.

[Solved] Amazon Workspaces Registration Service Failure

If you encounter an error indicating cannot connect to Amazon Workspaces’ Registration Services; well actually it has nothing to do with the network or connectivity issues. The error info is actually misleading.

Workspaces Unable to Connect Registration Service

Getting to the end of the topic to know about the fix; is to key in the new WORKSPACE REGISTRATION CODE. That can be found from the Amazon Management Console where the new Workspace was provisioned.


Once you grab the registration code; you can change it from the Workspace Application Options.

Manage Registrations


Once a proper registration code is specified; you are good to go if see all the checks passed.


After you complete your credentials configuration provided to you via. the email. You should be able to login to your newly launched Workspace Instance.


AWS Wish List : Set Query Filter VPC globally in AWS Management Console

This is yet another wish list for AWS Management Console‘s Usability Feature which I feel IMHO would improve the usability and controls the error & recreation of the VPC Components.

It is unimaginable to work without the Filtering the SELECTED VPC in production work loads in VPC Menu of AWS Management Console. I remember how my life would be for the project which had 4 VPC and each of it had 30+ Subnets by extension that many Route Tables and ACLs.  Having all the VPC components listed altogether gives the room for wrong configuring the network entities. It is very hard for humans to fully read between app-dmz-subnet-az1 and app-dmz-subnet-az2. The more horrifying reality is there is no UNDO.

I really should thank AWS team for continuously improving their services with new features and improvements. I would like to request and add the below to their list for AWS Management Console – Specifically for VPC Menu.

Current Setup :

There is a Dropdown Box which has the list of the VPCs running in that account in the selected Region. Selecting a VPC filters and shows only the components belonging to that VPC and this is applicable for all the entities [ Subnets, Route Tables, ACLs, Security Groups etc. ].

On a different note – a newly created (hence unattached) Internet Gateway wouldn’t show up if the VPC filter is ON.  This has trolled me hard time [it was a very long 5 mins. of searching and pondering in my life then.]

Problem :

Yes, the filter is applied across the board for the AWS Management console – except for the popup / dialog box to create a new entity. What happens is that, the state of the selected VPC filter isn’t showing up in the dialog box and by default the last created VPC.

VPC Filter


This would just surprise again where did my Subnet Go – I remember creating it just now.

Feature Request :

Continue the state of the currently applied VPC filter for the dialog boxes as well.