What should I do if my website slows down after clearing the domain's DNS cache?

　　In daily network operations, many users choose to clear their DNS cache when encountering website errors or domain name resolution problems. However, some people find that after clearing the DNS cache, website access speed not only doesn't improve, but actually slows down. This phenomenon confuses many users: shouldn't clearing the cache make website access faster? In fact, DNS caching is an important mechanism for improving access speed, and a decrease in speed after clearing it is normal, but there are ways to optimize the experience.

　　DNS is the internet's "phone book," translating user-entered domain names into IP addresses, enabling computers to correctly locate website servers. To improve access speed, operating systems, browsers, and network devices cache resolved DNS records; this is the DNS cache. When a user clears the DNS cache, the system deletes all saved domain-IP mapping records. This means that the next time any website is accessed, the system must re-send a resolution request to the DNS server. For a short period, due to the additional latency of DNS resolution, access speed may decrease, especially for users with high traffic or multiple websites.

　　Reasons for slower access after clearing the DNS cache:

　　1. Local cache is cleared. Clearing the DNS cache, After clearing the local cache, the local computer no longer retains any DNS records. Upon first access to a website, the system must re-query the DNS server. This increases access latency, especially when the DNS server is slow, resulting in a significant drop in access speed.

　　2. Slow ISP DNS server response: After clearing the local cache, all DNS requests are sent to the DNS server provided by the ISP. If the ISP's DNS server is not fast enough or is under heavy load during peak periods, website access speed will naturally decrease.

　　3. Excessively long TTL (Time To Live): TTL is the time a DNS record is stored in the cache. Even if the user clears the local cache, the ISP or intermediate DNS servers may still retain the original records. If the TTL is long, the old cache may affect resolution speed, leading to access latency.

　　4. CDN caching mechanism impact: Many websites use CDNs (Content Delivery Networks) to accelerate content loading. CDNs typically cache website resources and DNS resolution results. After clearing the local DNS cache, CDN nodes may need to reconfirm the user's geographical location and server node, resulting in increased latency on the first access.

　　5. Browser cache not synchronized: Besides the operating system's DNS cache, browsers also cache DNS records themselves. If the browser cache and the operating system cache are out of sync, old records may still be used after the DNS cache is cleared, or there may be delays in resolving DNS records.

　　6. Network environment or proxy impact. When using a company network, campus network, or proxy server, DNS requests may be forwarded through intermediate nodes. If network nodes are slow to respond, this can also lead to a decrease in access speed after clearing the DNS cache.

　　Optimization methods to improve website access speed:

　　1. Use a high-performance DNS server. Switching to a fast and stable public DNS server can significantly improve website resolution speed. After changing the DNS server, restart network devices or computers for the settings to take effect.

　　2. Use DNS pre-resolution. For website administrators, using the DNS pre-resolution tag in web pages can resolve domain names in advance, reducing initial access latency. The browser will perform a DNS lookup before loading the webpage, thereby improving user access speed.

　　3. Configure DNS records with appropriate TTL. For website operators, setting appropriate DNS record TTL values ​​is also crucial. A TTL that is too short will lead to frequent queries and increased latency; a TTL that is too long may result in untimely updates. It is generally recommended that the TTL be between 5 minutes and 1 hour, adjusted according to traffic volume and update frequency.

　　4. Use a CDN to accelerate access. A CDN distributes website content to nodes around the world, improving access speed. For cases where access speed is slow after clearing the DNS cache, CDN nodes will quickly deliver content based on the user's geographical location, thereby reducing latency.

　　5. Use both browser and system caches. After clearing the DNS cache, you can also clear the browser cache to avoid resolution conflicts or access delays. Common browsers such as Chrome, Firefox, and Edge all provide cache clearing functions.

　　6. Network optimization options. If slow access speed is related to network nodes or the ISP, consider changing the network environment, such as using fiber optic broadband or mobile data networks. Bypass the ISP's DNS caching or routing restrictions and choose faster nodes. For enterprise networks, a local area network DNS caching server can be configured to improve internal resolution speed.

　　7. Use DoH or DoT. These encrypted DNS technologies not only improve security but may also improve resolution speed. Encrypting DNS requests prevents ISP caching, hijacking, or pollution, ensuring accurate and fast resolution results.

　　While clearing the DNS cache is one way to resolve domain name resolution issues, it can also cause short-term access delays. Factors affecting access speed include local cache clearing, ISP DNS response, TTL settings, CDN mechanisms, and network environment. Optimizing DNS servers, configuring TTL, using CDNs, pre-resolving domain names, and network optimization can effectively alleviate slow access speeds. Understanding DNS caching mechanisms and their impact on access speed is a key step in improving web experience and website performance.