Gain insights into microservice principles, their pros and cons, Micro and Macro architecture, migration strategies, Docker's role, and technologies to effectively implement microservices.

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Microservices are one of the most important and popular software architecture trends. This architecture forms the base for a lot of companies including: Amazon, Netflix, Spotify, and Uber. 

In this course you’ll learn microservices in depth and understand reasons for and against microservices. Beyond that, you’ll learn about Micro and Macro architecture, strategies for migrating old systems, the role of Docker in this architecture, and technologies for implementing microservices. 

After taking this course, you’ll be better equipped to implement microservices for your own use.

An Introduction to Microservice Principles and Concepts

# Robustness

Microservice systems are more robust. 

When a memory leak exists in a microservice, only this microservice is affected and crashes. The other microservices keep running. Of course, they have to compensate for the failure of the crashed microservice; this is called **resilience**.

To achieve resilience, microservices can cache values and use them in case of a problem.  Alternatively, there might be a fallback to a simplified algorithm.

Without resilience, the **availability of a microservice system might be
a problem**.  It is likely that a microservice will fail for any reason.
- For example, due to the distribution into several processes, many more servers are involved in the system. Each of these servers can potentially fail.
- Communication between microservices occurs via the network, which can also fail. Therefore, microservices need to implement resilience to achieve robustness.




# Independent scaling


Most of the time, **scaling the whole system is not required**. For example, for a shop system during Christmas, the catalog might be
the most critical and hardware-consuming part. By scaling the complete system, the hardware is spent on parts that don't require more power.


**Each microservice can be independently scaled**. It is possible to start additional instances of a microservice and distribute the load of
the microservice into the instances. This can improve the scalability of a system significantly. 


So, in the previous example, just the catalog would need to be scaled up.
For this to work, the microservices
naturally have to fulfill **certain requirements**. For example, they must be stateless. Otherwise, requests of a specific client cannot be transferred to another
instance, because this instance then would not have the state specific to that client.

It can be difficult to start more instances of a deployment monolith due to the required hardware. Besides, building up an environment for a deployment monolith can be complex. This can require additional services or a complex infrastructure with databases and additional
software components.

In the case of a microservice, **the scaling can be more fine-grained** so that normally fewer additional services are necessary and the basic requirements are less complex.

In this lesson, we'll continue our discussion of the advantages of microservices.

Preface

Microservices

Micro and Macro Architecture

Migration

Docker

Technical Micro Architecture

Appendix

More on Advantages