What is a sticky session and when should I use one
A sticky session holds one exit IP for a defined period instead of rotating it on every request. Anything that spans more than one request and carries state should run on a sticky session.
Use a sticky session for
- Logging in and then browsing as that user
- Adding items to a cart and moving through checkout
- Any multi-page form or wizard
- Sites that bind their session cookie to the IP that created it
Use rotation instead for
- Independent page fetches where nothing carries over
- Search result pages
- Bulk product or listing collection
What breaks without one
Most sites tie their session cookie to the IP that first received it. If the IP changes mid-flow the site treats the request as hijacked, drops the session and sends you back to the login screen or an error page. That looks like an unreliable proxy, but it is the target enforcing its own session rules.
Practical advice
Pick the shortest sticky window that finishes your flow. Longer windows concentrate more traffic on one address, which is exactly what rate limiting is looking for.