# Operator fusion in RxJava 2

DevFeed: [Operator fusion in RxJava 2](<https://devfeed.tech/articles/operator-fusion-in-rxjava-2-38620.md>)

Original publisher: [Read original article](<https://krossovochkin.com/posts/2019_11_02_operator_fusion_in_rxjava_2/>)

Published: 2019-11-02T00:00:00Z

Content type: tutorial

Language: en

Sources: [Vasya Drobushkov](<https://devfeed.tech/sources/vasya-drobushkov.md>)

Topics: [RxJava](<https://devfeed.tech/topics/rxjava.md>), [Library](<https://devfeed.tech/topics/library.md>), [reactive](<https://devfeed.tech/topics/reactive.md>), [backpressure](<https://devfeed.tech/topics/backpressure.md>)

Tags: [2](<https://devfeed.tech/tags/2.md>), [article](<https://devfeed.tech/tags/article.md>), [backpressure](<https://devfeed.tech/tags/backpressure.md>), [flowable](<https://devfeed.tech/tags/flowable.md>), [memory](<https://devfeed.tech/tags/memory.md>), [overhead](<https://devfeed.tech/tags/overhead.md>), [performance](<https://devfeed.tech/tags/performance.md>), [reactive](<https://devfeed.tech/tags/reactive.md>), [rxjava](<https://devfeed.tech/tags/rxjava.md>), [technical](<https://devfeed.tech/tags/technical.md>)

## AI overview

This article explains operator fusion in RxJava 2 as an optimization intended to reduce performance and memory overhead. It first reviews Observable, Flowable, their related observer or subscriber types, and backpressure, then introduces the assembly and subscription stages of an Rx chain.

## Source excerpt

Introduction RxJava is a very powerful library, though it has some issues as well. Specifically performance and memory issues, which come from problems library tries to solve and how the solution is designed from technical perspective. In order to minimize overhead in RxJava there are a number of optimizations, which are called "operator fusion". And we'll talk about them in this article. But first let's recap how RxJava reactive types work and what issues they have.