What is difference between Microservices and Decentralized applications

Question

I am new to the decentralized application, after going through some articles I confused between the microservices and decentralized application. Can someone help me to understand the difference between them. I know that microservices can be built using spring boot & docker. Is there any other technology present to build it.I think Ethereum is used to develop the decentralized application. Can someone help me to understand the difference?

Answer 1

A microservice application still runs on your infrastructure, you still control all of its nodes, state and infrastructure. So, despite being distributed (and even though the infrastructure might not be yours such as a 3rd party cloud), you still have the power to interfere in all of its aspects.

The main selling point of a decentralized application is that theoretically no one can actually interfere in its infrastructure since it's not owned by a single entity. Theoretically anyone in the world (and the largest its user base, the more resilient the decentralized application becomes) can become a node in the infrastructure and the "current valid state" is calculated based on a kind of agreement between the nodes (so, unless you can interfere in a majority of the nodes, which you don't own, you can't change the application's state on your own).

In a certain sense, you're right that they seem similar, since they're both distributed applications. The decentralized ones just go a step further to be not "owned" and "controlled" by a single entity and be the product of an anonymous community.

EDIT

So suppose you/your company makes a very cool microservice application and you host it on a bunch of 3rd party clouds around the world to make sure it's very redundant and always available. A change of heart on your part (or maybe being forced to do so by government regulations) can shutdown the application out of the blue or ban certain users from it or edit/censor content currently being published on it. You're in full control since it's your app. As good as your intentions might be, you are a liability, a single point of failure in the ecosystem.

Now, if your app is decentralized... there's no specific person/entity to be hunt down to force such a behavior. You need to hunt thousands/millions of owners of single independent nodes providing infrastructure to the app and enforcing its agreed set of rules. So how would you go banning users / censoring content / etc? You (theoretically) can't... unless you can reach a majority of its nodes and that has already proven to be quite difficult and even brute force might be nearly impossible to achieve.

Answer 2

Microservice

Microservice is rather software architecture. The idea is that you have many small applications - microservices, each focused on addressing only a single goal, but doing it really well.

Specific instance of a microservice can be for example application running HTTP server for managing users. It could have HTTP endpoints for adding, viewing and deleting users in a database. You would then deploy such application together with database on some server.

With fair degree of simplification, we could say that microservice is not all that different than a web browser you are running on your computer. The difference between your web browser and a microservice is that microservice will be running on server, exposing some sort of network interface, whereas you browser runs on your personal computer and it doesn't expose network interface for others to interact with.

The bottom line is that singe microservice is just an application running on a server, you can modify its code anytime, you can stop it any time, you can change data in the database it's using.

Decentralized application

Decentralized application is deployed to blockchain. Blockchain is network of computers (Ethereum MainNet has tens of thousands of nodes), all running the same program. When you write decentralized application (called smart contract, in terms of Ethereum blockchain) and you "deploy it", what happens is that you basically insert your code into this networks of computers and each of them will have it available.

Once code of your application is in the network, you can interact with it - you can the interface you defined in your decentralized application, by sending JSON-RPC requests to a server which is part of this blockchain network.

It then takes some time until your request for execution is picked up by network. If everything goes right, your request is eventually distributed to the network and executed by every single computer connected to blockchain.

The consequence of that is that if some computer in the network tries to lie about the result, the fraudulent attempt would be noticed by the rest of the network.

The bottom line here is that decentralized application is not executed on one computer, but many (possibly thousands) and even as a creator, you cannot modify it's code or data (you can only to limited degree)