CDN (Content Delivery Network) Explained

 Let's discuss about CDN in details and below are the points you would consider generally while serving static pages, images etc.

Use-case

• An example of your server serving static and dyanamic html pages, images etc.

Caching

• To make it more fast and efficient, first approach you would take is cache the details and serve it accordingly.

Device Customised Data

• Different type of html pages and images that would serve to different devices (desktop, mobile etc). Let's say 5 diff devices and 100 diff countries so 1000 diff data points to be served by cache.

Performance Consideration

• You want to serve your pages fast to the users else they would lose interest in the product if it takes time to load.

Global Cache

• You would cache the information outside server to serve the content fast and to avoid single point of failure, you would go with distributed cache and data is spread across multiple servers of cache.

Shard Caches

• To serve the requests even faster considering many combinations like 1000 data points discussed above, you might go with sharding and shard it based on locations, countries etc and diff type of request like probably request from US would go to diff set of cache box which would serve US related requests etc.

Localized Caches

• One more problem would be let's say company is from US and cache servers are sitting in US and our user-base is across countries so to serve requests efficiently for diff countries etc we have to make localised cache say for India one data centre in India to serve requests and so on.

Why should you use a CDN?

• Well If you have to design by your own, you have to take case of all above points and majorly concluded as below
• Available in different countries
• Follows regulations
• Serves the latest content

What are the benefits of a CDN?

• Specialised solution like CDN takes care of all of the above points and you can focus on your business logics to expand it further.
• One of the good example if Akamai and specialiases in as below
• Hosting boxes close to the users.
• Follow regulations
• Allow posting content in the boxes via UI.
• Expiry time in CDNs
• Something like sometime you need cache for 60 sec or 60 min only etc. Everything handled provided via UI.
• Another good example for the same is Amazon S3.
• Super cheap
• Very reliable
• Easy to use

In details explanation of CDN : https://learnwithnitin.blogspot.com/2014/02/content-delivery-network-cdn.html

Happy Learning :) 

Why do Databases fail? AntiPatterns to avoid !

Databases are often used to store various types of information, but one case where it becomes an a problem is when being used as a message broker.

The database is rarely designed to deal with messaging features, and hence is a poor substitute of a specialized message queue. When designing a system, this pattern is considered an anti pattern. 

Here are possible drawbacks:

• Polling intervals have to be set correctly. Too long makes the system is inefficient. Too short makes the database undergo heavy read load.
• Read and write operation heavy DB. Usually, they are good at one of the two.
• Manual delete procedures to be written to remove read messages.
• Scaling is difficult conceptually and physically.

Disadvantages of a Message Queue:

• Adds more moving parts to the system.
• Cost of setting up the MQ along with training is large.
• Maybe be overkill for a small service.

It is important to be able to reason why or why not a system needs a message queue. These reasons allow us to argue on the merits and demerits of the two approaches.

However, there are blogs on why Databases are perfectly fine as message queues too. A deep understanding of the pros and cons helps evaluate how effective they would be for a given scenario. 

In general, for a small application, databases are fine as they bring no additional moving part to the system. For complex message sending requirements, it is useful to have an abstraction such as a message queue handle message delivery for us.