Question: How do I troubleshoot and reduce increased latency from CloudFront?

I'm seeing increased latency in responses from Amazon CloudFront. How can I identify the cause and reduce latency?Short descriptionTo troubleshoot latency from CloudFront, first identify which of the following events are contributing to the latency:The time taken for requests to go between the Client and the CloudFront edge locations. This includes the Domain Name System (DNS) lookup process and TCP and SSL/TLS negotiations.The time taken for requests to go between CloudFront and the origin. This includes the origin DNS lookup process, TCP and SSL/TLS negotiations with the origin, and time taken by the origin to process and respond with an object.Then, follow the troubleshooting steps for the events that are causing the most latency.

ResolutionIdentify events causing latency from CloudFront:To identify which events are causing latency from CloudFront, do one of the following:Run the following cURL command:curl -w "DNS_resolution: %{time_namelookup}| TCP_negotiation_time: %{time_connect}| SSL_negotiation_time: %{time_appconnect}| TTFB: %{time_starttransfer}| Total time: %{time_total} \n" -o /dev/null -vsL https://www.example.comNote: Replace example.com with your CloudFront domain name or alternate domain name (CNAME) and URL path.Check how long each stage of a network request takes in the developer tools of your web browser. For example, if you're using Mozilla Firefox, the Timing tab provides this information.Based on the time-taken for each event or request, see the related Resolution section in this article.If you observed latency in the past, then check the fields time-taken and time-to-first-byte in the CloudFront access logs. CloudFront access logs don't log the time taken by the client for the DNS lookup process and TCP and SSL/TLS negotiationsReducing latency in DNS resolutionIncrease DNS caching time in the client-side DNS.Increase the Time to Live (TTL) of the cache in the local DNS server.Increase the TTL on the DNS record in your DNS registrar/provider.If the resolver DNS server from your internet service provider is causing latency, then consider using public DNS servers.Reducing latency in TCP and SSL/TLS - Negotiation timeCheck your local network bandwidth and internet bandwidth.Check if there are any network disruption in your internet server provider or router.Optimize your local network performance through your internet service provider or network routes.Confirm you're using the correct DNS resolver that allows your web browser to find the closest and correct POP location.To improve HTTPS site performance, keep your certification chain short.Latency can be caused by a firewall, proxy, or local router. To determine which of these is causing latency, run the following MTR command from your system. See Diagnosing Network Issues with MTR for more information.mtr -rw example.com --no-dnsNote: Replaceexample.com with your domain name.Reducing latency in Time Taken for First Byte (TTFB) and Total Time Taken (TTL)If CloudFront returns "X-Cache:Hit from cloudfront"CloudFront returns "X-Cache:Hit from cloudfront" when requests are served from the closest edge location. To reduce latency:Turn on CloudFront automatic compression to compress files and increase download speed.Use local or browser caching to reduce requests to CloudFront. Specify cache-control header on the files to instruct web browsers to keep the website content in the browser's memory or the local disk for a certain amount of time. For more information on cache-control headers, see Specifying the amount of time that CloudFront caches objects.If CloudFront returns "X-Cache:Miss from cloudfront"If CloudFront returns "X-Cache:Miss from cloudfront" when the request is sent to the origin. To reduce latency:Reduce the Round trip time (RTT) between CloudFront edge location to your origin location. If a request from a CloudFront edge location goes to the nearest origin location, then the RTT is less. However, TTFB is affected if the request is from an edge location geographically distant from the origin. To optimize the RTT, replicate origin server in multiple regions that are geographically closer to your users. Then, set up the DNS of your origin domain name so that it routes the request to origin servers based on latency or geolocation. If you're using Amazon Route 53 as your DNS provider, then see Choosing a routing policy for more information.Turn on CloudFront automatic compression to compress files and reduce download speed. If your file format is not supported by CloudFront Automatic Compression, then pre-compress that file in your origin and serve it with Content-Encoding header.Check the latency from the origin to CloudFront by enabling the Origin latency metric. Note: Standard CloudWatch rates apply.Turn on CloudFront Origin Shield.Add Response headers policies with Server-Timing header feature turned on. This feature can help you understand the events that are contributing to the latency between CloudFront and the origin.

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