What Is Proxy IP Caching? Which Requests Can Be Reused?

<p style="line-height: 2;"><span style="font-size: 16px;">In proxy IP usage, caching is an easily overlooked but highly impactful factor. Many people only focus on whether the IP is available and whether the speed is fast enough, while ignoring whether the request itself can reuse cached results. The result: data that only needs to be fetched once is repeatedly requested because of proxy rotation; or conversely, fresh data is needed, but an expired cache is retrieved because of connection reuse.</span></p><p style="line-height: 2;"><span style="font-size: 16px;">Caching in proxy scenarios is more complex than direct connections, involving TCP connections, HTTP responses, DNS resolution, session state, and possible caching on the proxy server side. Only by understanding these layers can you determine which requests can be reused and which must be re-initiated.</span></p><p style="line-height: 2;"><br></p><h2 style="line-height: 2;"><span style="font-size: 24px;"><strong>What Is TCP Connection Reuse?</strong></span></h2><p style="line-height: 2;"><span style="font-size: 16px;">TCP connection reuse is the most basic form of caching. Once a TCP connection is established, it can carry multiple HTTP requests. In direct connection scenarios, as long as the target domain is the same, the connection can be reused. In proxy scenarios, the situation is different.</span></p><p style="line-height: 2;"><span style="font-size: 16px;">With sticky sessions, the exit IP remains unchanged within the session window, so multiple requests to the same target domain can reuse the same TCP connection, reducing handshake overhead. B2Proxy's </span><a href="https://www.b2proxy.com/product/residential-proxies" target="_blank"><span style="color: rgb(9, 109, 217); font-size: 16px;">residential proxies</span></a><span style="font-size: 16px;"> support sticky sessions, and the window duration can be configured per task, making them suitable for collection tasks that require connection reuse. With rotating sessions, each request may be sent from a different exit IP. TCP connections are bound to a specific source IP; when the exit IP changes, the original connection can no longer be used and must be re-established.</span></p><p style="line-height: 2;"><span style="font-size: 16px;">Even with sticky sessions, when the window expires and the exit IP switches, the original connection becomes invalid. The sticky window duration directly determines the upper limit of connection reuse.</span></p><p style="line-height: 2;"><br></p><h2 style="line-height: 2;"><span style="font-size: 24px;"><strong>How to Use HTTP Response Caching?</strong></span></h2><p style="line-height: 2;"><span style="font-size: 16px;">The HTTP protocol itself has a caching mechanism, controlled by headers such as Cache-Control, ETag, and Last-Modified. But in proxy scenarios, caching becomes more complicated.</span></p><p style="line-height: 2;"><span style="font-size: 16px;">Proxies may modify request or response headers, stripping cache-related headers, causing clients to be unable to cache correctly. Changes in exit IP also affect CDN cache hits. With residential proxies, each request may come from a different region's IP. CDNs treat these requests as different users and may assign them to different edge nodes, reducing cache hit rates.</span></p><p style="line-height: 2;"><span style="font-size: 16px;">Static resources (images, CSS, JS) and API responses without real-time requirements are suitable for reuse when the proxy session is stable. Authenticated requests, POST requests, requests requiring real-time data, and responses explicitly set with no-cache must be re-initiated. B2Proxy's rotating session mode ensures that each request uses a different exit IP, making it suitable for scenarios that require forced refresh and avoiding cache interference.</span></p><p style="line-height: 2;"><br></p><h2 style="line-height: 2;"><span style="font-size: 24px;"><strong>When Should DNS Cache Be Cleared?</strong></span></h2><p style="line-height: 2;"><span style="font-size: 16px;">DNS resolution also has caching. With local resolution, the client resolves the domain first, and the local DNS cache affects the result. With remote resolution, the proxy server handles resolution, and the proxy's DNS cache affects the result.</span></p><p style="line-height: 2;"><span style="font-size: 16px;">When changing proxy providers, when the target website changes CDN, or when requests are always sent to the wrong geographic location, you need to check the DNS cache. In multi-region collection scenarios, remote resolution is usually more reliable because it uses the DNS of the proxy's location, which is closer to the real resolution result of the target market.</span></p><p style="line-height: 2;"><br></p><h2 style="line-height: 2;"><span style="font-size: 24px;"><strong>How to Reuse Session and Cookie Caching?</strong></span></h2><p style="line-height: 2;"><span style="font-size: 16px;">In scenarios requiring login state, cookies and session state must be reused. If the exit IP changes frequently, the server will consider the session abnormal and require re-login. Within the sticky session window, cookies, session IDs, and CSRF tokens can all be reused. The server sees a continuous session and will not trigger additional verification.</span></p><p style="line-height: 2;"><span style="font-size: 16px;">After the sticky window expires or the session ID is actively switched, the original session state may become invalid, requiring re-login. For long-cycle tasks, it is recommended to split the task into multiple short sessions, save progress after each session, and then start a new session to continue.</span></p><p style="line-height: 2;"><br></p><h2 style="line-height: 2;"><span style="font-size: 24px;"><strong>Does Proxy Server-Side Caching Exist?</strong></span></h2><p style="line-height: 2;"><span style="font-size: 16px;">Some proxy providers cache responses at the gateway level, especially for static resources. This kind of caching is transparent to users and cannot be controlled. Legitimate proxies generally do not cache the response content of user requests because it raises privacy and accuracy issues. If you find that the same request returns obviously expired data, you can bypass it by adding random query parameters or using different request headers.</span></p><p style="line-height: 2;"><br></p><h2 style="line-height: 2;"><span style="font-size: 24px;"><strong>How to Design a Cache-Friendly Collection Strategy?</strong></span></h2><p style="line-height: 2;"><span style="font-size: 16px;">Distinguish task types. Use sticky sessions for static resources and unchanging data, allowing connection and response caching to take effect. Use rotating sessions for requests requiring real-time data, ensuring that each request is re-initiated.</span></p><p style="line-height: 2;"><span style="font-size: 16px;">Set the sticky window reasonably. The window should cover the complete cycle of a single task, but should not be too long, avoiding session interruption caused by unstable exit IPs.</span></p><p style="line-height: 2;"><span style="font-size: 16px;">Explicitly control cache headers. Set Cache-Control: no-cache or If-None-Match as needed to clearly tell the server the caching behavior you need.</span></p><p style="line-height: 2;"><span style="font-size: 16px;">Monitor cache hit rates. An abnormally low hit rate may be caused by CDN cache invalidation due to proxy IP changes, or by the proxy modifying cache headers.</span></p><p style="line-height: 2;"><span style="font-size: 16px;">Do not rely on proxy server-side caching. All caching should be explicitly managed on the client side or in your collection system.</span></p><p style="line-height: 2;"><br></p><p style="line-height: 2;"><span style="font-size: 24px;"><strong>Conclusion</strong></span><span style="font-size: 16px;"><br>Proxy IP caching involves TCP connections, HTTP responses, DNS resolution, and session state. Which requests can be reused depends on the proxy mode and the nature of the request .</span></p><p style="line-height: 2;"><span style="font-size: 16px;">Sticky sessions are suitable for tasks requiring connection reuse, response caching, and session persistence; rotating sessions are suitable for tasks requiring distributed requests and fresh data. B2Proxy offers three types of residential proxy products:residential proxies, </span><a href="https://www.b2proxy.com/product/isp-proxies" target="_blank"><span style="color: rgb(9, 109, 217); font-size: 16px;">static residential proxies</span></a><span style="font-size: 16px;">, and unlimited residential proxies. They support rotating and sticky sessions, as well as region and ASN targeting, and can be flexibly configured according to task type, helping to find a balance between cache reuse and data freshness. Finding a balance between reuse and re-initiation will significantly improve the efficiency and data quality of proxy IPs.</span></p>