Sticky Session
A load balancer feature that routes all requests from the same client to the same backend server. Needed when servers store session state locally.
What is Sticky Session?
A load balancer feature that routes all requests from the same client to the same backend server. Needed when servers store session state locally.
Sticky Session is a foundational concept that sits in the Load Balancing & Proxies area of system design. Engineers reach for it whenever they need to reason about real-world trade-offs in that space — not just for textbook correctness, but because real production systems at companies like Netflix, Amazon, and Google make these decisions every day.
If you want to go deeper than this definition — with diagrams, code, and a quiz to lock it in — work through the "Sticky Session" lesson linked below. It walks through the why, the mechanism, the trade-offs, and how the giants actually use it in production.
Learn Sticky Session in depth
Full interactive lesson with diagrams, code examples, real-world references, and a quiz.
Open the Sticky Session lessonRelated lessons
Lessons that touch on Sticky Session as part of a larger topic.
Monotonic Reads
Once you have seen a value, you never see an older one, the minimum useful consistency guarantee
advanced · consistency models
Sticky Sessions
Pinning users to the same server, when stateless just isn't possible
foundation · load balancing proxies
Read-Your-Writes
You always see your own updates immediately, the consistency users expect but rarely get by default
advanced · consistency models
Session Affinity
The broader concept behind sticky sessions, soft preferences vs. Hard pinning
foundation · load balancing proxies
Distributed Session Management
Managing user sessions across multiple servers, sticky sessions, centralized stores, and token-based approaches
intermediate · security architecture
See also
Related glossary terms you might want to look up next.
Load Balancer
Distributes incoming traffic across multiple servers so no single server gets overwhelmed. Like a traffic cop directing cars to different lanes.
Session
A way to maintain state across multiple HTTP requests. The server stores data about a user and gives them a session ID (usually in a cookie).
Stateful
A system that remembers previous interactions. The server keeps track of client state between requests, making it harder to scale but sometimes necessary.