Inside Netflix’s Scalable Backend: Microservices, CDN, and Data Pipelines

Overview

Netflix accounts for about 15% of global internet bandwidth and delivers over 60 billion hours of content per month. Building a robust, highly scalable, reliable and efficient backend is a massive engineering effort, which Netflix’s team has solved.

System Overview

Netflix runs on both Amazon Web Services and its own Open Connect CDN. The system consists of three main parts:

Open Connect Appliances (OCA) – Netflix‑built global CDN placed in ISP and IXP networks to deliver content.

Client – Devices (smart TVs, Android, iOS, consoles) that run Netflix applications, e.g., the web UI built with React.

Backend – Databases, servers, logging, monitoring, recommendation engine and other services running on AWS.

Backend Architecture Details

Netflix is a pioneer of micro‑service architecture. Each component is a loosely‑coupled service, enabling rapid, frequent and reliable delivery of large, complex applications.

Typical request flow:

Client sends a playback request to the backend behind an AWS Elastic Load Balancer (ELB).

ELB forwards the request to the API Gateway (Zuul).

Zuul routes to the appropriate API (Signup, Discovery/Recommendation, Play, etc.).

The API invokes one or more micro‑services, which may read/write data stores, emit events to streaming pipelines, or call other services.

Micro‑services are stateless and can run thousands of instances.

Events are sent to Kafka for real‑time processing or batch analytics.

Processed data may be persisted to S3, HDFS, Cassandra, and other stores.

Zuul2 API Gateway

Netflix uses Amazon ELB to balance traffic to Zuul, an open‑source API gateway that provides dynamic routing, traffic monitoring, security, and fault‑tolerant edge computing. Zuul supports inbound, node and outbound filters to add authentication, routing, static responses, or modify headers.

Typical API categories:

Signup API – Handles registration, billing, trial.

Discovery API – Handles search and recommendation requests.

Play API – Handles streaming, license checks and playback.

Titus Container Management

Titus is a container management platform built on Apache Mesos that runs thousands of EC2 instances and launches hundreds of thousands of containers daily. It can be viewed as Netflix’s internal version of Kubernetes.

Data Storage and EVCache

EVCache is a memcached‑based caching layer deployed on AWS EC2 to provide fast access to frequently used data and to reduce load on backend stores. Netflix also uses MySQL for billing, Cassandra for user metrics and viewing history, and SSD‑backed caches to reduce memory costs.

EVCache architecture:

Cassandra

Cassandra is an open‑source distributed wide‑column NoSQL database used for high‑availability, fault‑tolerant storage of metrics, viewing history and other user data across multiple regions.

Streaming Pipeline

Netflix processes trillions of events per day using Apache Kafka, Apache Spark and other stream‑processing tools. Events from services such as Beacon are ingested into Kafka, analyzed in real time for personalization, monitoring and business intelligence.

Conclusion

The article provides a detailed analysis of Netflix’s backend architecture, offering insights for developers and architects.

References

Titus Overview – https://netflix.github.io/titus/overview/

Zuul2 Open‑Source – https://netflixtechblog.com/open-sourcing-zuul-2-82ea476cb2b3

Open Connect Overview – https://openconnect.netflix.com/Open-Connect-Overview.pdf

How Netflix Backend Operates – https://www.nexsoftsys.com/articles/how-netflix-backend-system-operates.html

Hystrix Explained – https://riteeksrivastava.medium.com/hystrix-what-is-it-and-why-is-it-used-f84614c8df5e

Engineering Trade‑offs and Netflix API Re‑architecture – https://netflixtechblog.com/engineering-trade-offs-and-the-netflix-api-re-architecture-64f122b277dd

Application Data Caching Using SSDs – https://netflixtechblog.com/application-data-caching-using-ssds-5bf25df851ef

Evolution of Application Data Caching from RAM to SSD – https://netflixtechblog.com/evolution-of-application-data-caching-from-ram-to-ssd-a33d6fa7a690

Optimizing the Netflix API – https://netflixtechblog.com/optimizing-the-netflix-api-5c9ac715cf19