Traditional Architecture:

Monolithic means composed all in one piece. Software is designed to be self-contained meaning having all that is needed, in itself. There are many layers in monolithic architecture.
- front-end (user-interact)
- business layer (logic)
- data access layer (data interaction)

Problems:
They have slow release cycles and are updated relaitvely infrequently.
Once new release get ready, developers package up the whole system and hand it over to the Ops Team, who then deploys and monitors it.
In case of hardware failures, the Ops Team manually migrates it to the remaining healthy servers.

Micro-service Architecture:

This architecture is used to divide the whole monolithic app into small applications and make it independent. Micro-Service architecture is concept of breaking down big monolithic app into smaller independent app. component. Micro-services are developed from each other. They can be developed, deployed, updated and scaled individually. Change to any component is convenient and new technology can be adopt where needed which provides easy to operation team.

Complexities:
How to handle? This is not easy to handle the multiple small applications and to transfer data between them and manage error. In bigger micro-services architecture, it is very difficult to configure, manager and keep the whole system running smoothly. Adjusting micro-services in a manner where you can achieve maximum hardware resource utilization is also a challenge. Making sure all services are working is also not easy. Doing all this manually is hard work. So, we need automation which includes automatic scheduling of those components to our servers, automatic configuration, supervision and failure handling.

This is where Kubernetes comes into action.

Deploy your application through automation on server and do not need operations team after deploying kubernetes and user can use it easily. Kubernetes help in hardware fail for Ops team and schedule those apps in the event of a hardware failure and automatically monitor those apps.