41 lines
2.5 KiB
Markdown
41 lines
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# Application layer
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## Application layer - Introduction
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[Source: Intro to architecting systems for scale](http://lethain.com/introduction-to-architecting-systems-for-scale/#platform_layer)
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Separating out the web layer from the application layer (also known as platform layer) allows you to scale and configure both layers independently. Adding a new API results in adding application servers without necessarily adding additional web servers.
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The single responsibility principle advocates for small and autonomous services that work together. Small teams with small services can plan more aggressively for rapid growth.
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Workers in the application layer also help enable [asynchronism](https://github.com/donnemartin/system-design-primer#asynchronism) .
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## Microservices
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Related to this discussion are [microservices](https://en.wikipedia.org/wiki/Microservices) , which can be described as a suite of independently deployable, small, modular services. Each service runs a unique process and communicates through a well-definied, lightweight mechanism to serve a business goal. [1](https://smartbear.com/learn/api-design/what-are-microservices)
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Pinterest, for example, could have the following microservices: user profile, follower, feed, search, photo upload, etc.
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## Service Discovery
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Systems such as [Zookeeper](http://www.slideshare.net/sauravhaloi/introduction-to-apache-zookeeper) can help services find each other by keeping track of registered names, addresses, ports, etc.
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## Disadvantage(s) : application layer
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- Adding an application layer with loosely coupled services requires a different approach from an architectural, operations, and process viewpoint (vs a monolithic system) .
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- Microservices can add complexity in terms of deployments and operations.
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## Source(s) and further reading
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- [Intro to architecting systems for scale](http://lethain.com/introduction-to-architecting-systems-for-scale)
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- [Crack the system design interview](http://www.puncsky.com/blog/2016/02/14/crack-the-system-design-interview/)
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- [Service oriented architecture](https://en.wikipedia.org/wiki/Service-oriented_architecture)
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- [Introduction to Zookeeper](http://www.slideshare.net/sauravhaloi/introduction-to-apache-zookeeper)
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- [Here's what you need to know about building microservices](https://cloudncode.wordpress.com/2016/07/22/msa-getting-started/) |