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Few months back, I had to make some changes to design of Communication Service. It was quite a complex architecture overall and I thought of documenting this in blogpost to outline my thought process. A communication service is responsible for reliably delivering the customer notification to the end user via any channel. In our case, the channels were email, SMS and push notification. The communication service was divided into multiple microservices: Communication Services This was...

In a complex multiple microservices architecture, especially where in one microservice ends up calling a chain of other microservices, the API latency can become a concern. This is because there is network hop at each microservice layer, which adds to the latency in addition to the actual logic executed by the microservice itself. For example, in an e-commerce application, an Add to Cart API request might end up calling multiple downstream microservices such as Pricing...

Recently, we migrated a large MySQL database containing GB’s of data, millions of rows in few tables to CosmosDB. This was done without downtime. I want to lay down the approach we took in this post. Our intention was to setup both the database active - active and incrementally shift the traffic point to Service v1 (which was reading/writing to MySQL) towards Service v2 (which was reading/writing to CosmosDB) The first challenge was doing the...

Many organizations aggregate their logs on Splunk, which is a popular product for data ingestion and building intelligence on top of it. I too have been playing with data hosted on Splunk in last few weeks. Recently, I encountered a problem, where-in the data needs to be extracted based on some specified condition within a JSON array. For example, the splunk record was as follows: { "name": "Test Name", "id": "ac646022-fa55-4e04-9856-a25a41b30014", "phases": [ { "name":...

Here are a few useful kubernetes commands: Login into the one of the pod’s shell kubectl exec --stdin --tty <<pod>> -- /bin/bash View services from all namespaces kubectl get service --all-namespaces Change the current namespace context kubectl config set-context --current --namespace = <<namespace>> Describe a pod kubectl describe <<pod>>

Distributed transactions rollback are a tough beast. There are many patterns to solve this such as: Two-phase commit Saga pattern In this post, we will look at one of the example of a problem and how to solve it using the Saga pattern. Let’s say, we are an e-commerce platform and building a backend service for taking and submitting orders. A typical flow would like this: Now, Just assume, what would happen if an intermittent...

Many a times, when we want to display multiple images of various aspect ratios and pixel sizes in a gallery. In that case, there will be a single height and width of the card for the container, however the images will be of multiple sizes. This can result in whitespace around the container as follows: One of the ways to solve it is to add the blur around the image. This is how it can...

Some of the better useful open source Angular libraries NgSelect NgxCharts Ng Bootstrap

We were working on a proof of concept and for that I quickly needed a HashMap with a Time to Live (TTL). Basically, I wanted the keys to expire automatically after a certain time period. Fortunatly, Google Guava provides this out of the box in form of LoadingCache Here is how you would initialize it, private LoadingCache<String, String> cache = CacheBuilder.newBuilder() .maximumSize(Integer.MAX_VALUE) .expireAfterWrite(5, TimeUnit.MINUTES) .build(new CacheLoader<String, String>() { @Override public String load(final String response) throws...

I have been recently focused a lot on Web application security especially web vulnerabilities such as Cross Site Scripting (XSS) and Cross Site Request Forgery (CSRF) One of the interesting protection mechanism around these attacks is Same Origin Policy which I believe every application developer should understand in deep. So what is cross origin policy? Reference: Mozilla docs When a browser loads the web page, the web page elements might refer to other origins (basically...