Three seconds may not seem like a long time, but it could be the difference between making the online sale and losing a customer.

According to Radware's STATE OF THE UNION: Ecommerce Page Speed & Web Performance – Spring 2015: “By 2010, 57% of online shoppers stated that they would abandon a web page after waiting 3 seconds for it to load. Three seconds. In case study after case study, this is the point at which most visitors will bounce if a page is not loading quickly enough. Not coincidentally, case study after case study shows that this is when business metrics – from page views to revenue – are affected by slow page rendering. Whether your goal is to convert browsers into buyers or ensure that your content is served to as many eyeballs as possible, your eye should be on this 3-second target.”

But then again, it is not only about 3 seconds, but rather about overall responsiveness, as Ron Lifton, Senior Solutions Marketing Manager, NetScout Systems, points out: “From manufacturing to highly competitive arenas such as retail banking, insurance and travel, every millisecond of responsiveness on the Web site counts.”

“Website visitors hate delay and the impact of slow response times on revenue have been well documented,” Frank Puranik, Senior Technical Specialist at iTrinegy, clarifies. “For example, Amazon calculated that a page load slowdown of just one second could cost it $1.6 billion in sales each year.”

Even for websites that are not Amazon, web response time can have a major impact on revenue. Hopefully this compilation of expert testimony will give you a little more insight into what to watch out for.

In this list, APMdigest asked industry experts – from analysts and consultants to the top vendors – to outline the most important factors that impact website response time. Each expert has given their opinion on which factor is the most significant, and the result is a well-rounded list that encompasses a wide variety of issues that can impact performance.

As often happens with these types of lists on APMdigest, many of the factors overlap and potentially fit into multiple categories. But the purpose of the list is not necessarily to relegate these issues to tidy stand-alone categories, but rather to highlight the many diverse and often interrelated factors that can impact website performance. Some of these factors are well-known issues that impact web performance, while others may open your eyes to issues you might not have thought about before.

The full list of 20 Factors That Impact Website Response Time will be posted in 4 parts over the next 4 weekdays. With factors 1–5, we start with the high level view.

1. COMPLEXITY

Complexity is the number one factor influencing website response time. Today’s modern websites are in effect highly componentized applications built from an ever-growing mix of third-party services, cloud-based computing and self-hosted infrastructure. This rise in complexity increases potential points of failure and makes troubleshooting performance with specialized tools more challenging. This is why effective APM solutions must measure end user experience and in context of that, proactively and easily indicate what supporting infrastructure or service is inhibiting optimal quality.
Aruna Ravichandran
VP Marketing, CA Product and Solutions Marketing, CA Technologies

Complexity is the number one factor that impacts response time. Too often, organizations get wrapped up in adding so much functionality that performance actually suffers. Complexity can be on the client side as well as the application side. Applications can be distributed across data centers or the cloud and can utilize a variety of technologies and platforms. Code level complexity is difficult and costly to diagnose without access to tools which provide gap free data. From a customer's perspective, it’s best to think about what a site doesn’t need - and how to simplify and streamline instead. A function that comes at the cost of performance does more harm than good.”
David Jones
APM Evangelist, Dynatrace

Fast web-response time is absolutely critical to digital business. The bourgeoning complexity of the infrastructure supporting these web applications and services has become unmanageable for many IT organizations. Without clear insight into how applications relate to infrastructure, IT lacks the visibility to assess the level of impact and to find and fix problems quickly. The result is an unpredictable and often unsatisfactory user experience. This is a pervasive problem – and one that APM solutions, which unify the perspective of both application and infrastructure are uniquely poised to solve.
Bill Berutti
President, Performance & Availability and Cloud Management/Data Center Automation, BMC Software

In modern web sites the top reason contributing to slow responses time relies in the client side complexity. While server requests are can be optimized in various ways (like with parallel processing, asynchronous operations etc.) modern web sites rely heavily on client side JavaScript execution, smart caching and sometimes 3rd parties content. Access from different browsers on different devices including mobile with different resources and OS makes it challenging for the frontend developers to optimize their site performance. In order to improve your web site experience for the all end users you must start by measuring the real user experience from the end user browsers and devices.
Amichai Ungar
Product Manager, HP Software

Application complexity and lack of visibility create gaps where optimizations can occur. There are too many factors and often the siloed organizations and tools prevent performance tuning from occurring. Inefficiencies most often occur in the code and the database, but factors such as storage and network can be a factor.
Jonah Kowall
VP of Market Development and Insights, AppDynamics

The top factor is complexity. Websites today are complex, business-critical systems, with hundreds of elements that require discipline and the right tooling to manage. They need to be responsive and adapt to multiple devices, often with a dozen or more JavaScript plugins, many of them from third parties, that span analytics to customer ratings. Websites need to be global, often serving customers from multiple datacenters, using dynamic DNS, CDNs and other caching tools. The back-end infrastructure is also getting more complex with dynamically scaling cloud architectures. The implication of all this complexity is the challenge in managing it: paying attention to all the elements, understanding each component’s contribution to page load times and quickly diagnosing the root cause of performance issues.
Gerardo Dada
VP, Product Marketing and Strategy for Pingdom by SolarWinds Cloud

Although no single factor conditions the speed of website response, a key contributor is the number and latency of synchronous browser requests.
Larry Haig
Senior Consultant, Intechnica

The root cause behind performance issues in a web services delivery environment can be very complex and involve the network, transport, servers, service enablers (like DNS), n-tier applications, and QoS.
Ron Lifton
Senior Solutions Marketing Manager, NetScout Systems

2. INTERDEPENDENCIES

The top factor impacting website response time is application/infrastructure/endpoint interdependencies. Shifting dynamics across these interdependencies can cause latencies, outages, security breaches and wreak havoc on end user experience.
Dennis Drogseth
VP of Research, Enterprise Management Associates (EMA)

3. CONFIGURATION AND COMMUNICATION OF COMPONENTS

Today's website infrastructure consists of a lot of components. Some of these components aren't even located in the same country. The installation and configuration of these components is the biggest factor of slow website response times. The response time of the website is as good as the weakest link and in my experience this usually resides in the communication and configuration of components. Gaining visibility in the configuration and the communication is crucial in detecting the root cause for these slow response times.
Coen Meerbeek
Online Performance Consultant and Founder of Blue Factory Internet

4. LATENCY

The top factor that impacts website response time is latency. While mean time between failure (MTBF) and mean time to repair (MTTR) are critical metrics for front-end application performance, time to first byte (TTFB) is speed metric that drives satisfactory user experience and search rankings. TTFB is the time it takes for your browser to receive the first byte of response from a web server. A platform approach that unifies monitoring of servers and back-end infrastructure and front-end API and application performance is the key to ensuring speed and responsiveness that meet user expectations.
Gabe Lowy
Technology Analyst and Founder of TechTonics Advisors

We find that latency has one of the biggest negative impacts on website response time — in other words, the distance from the website origin server to the user who is accessing the website. Organizations can get around this by either building data centers (or locating and managing servers) in many locations throughout the world or partnering with a content delivery network (CDN) that has already built a high speed network with points of presence in all of the locations the organization needs to reach customers and employees.
John McIlwain
Director of Product Management, CDNetworks

5. DEMAND PEAKS

Scaling is an critical factor that impacts website response time. When problems rear their ugly head it's typically during peak times. Think Black Friday or Cyber Monday. These may be extreme examples but they illustrate a very good point. Infrastructure must be to be scaled to handle peak rates rather than average rates. Peaks in demand may only last for a short time, sometimes only milliseconds but they have a much longer lasting effect, impacting not only the web server and supporting systems but more importantly user experience. To scale the infrastructure accordingly, real-time instrumentation with sub-second granularity is key to understanding these transient peaks and the behavior of each component during these times.
James Wylie
Director of Technical Product Marketing, Corvil

Read Part 2 of "20 Top Factors That Impact Website Response Time"