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High Traffic Surges Got Your Website Down? Here’s Why

by Martin Larsen, on 5/30/19

A surge in traffic is in many ways a dream for any website. After all, more traffic means more customers and more sales.

However, you can sometimes do your job too well when your successful marketing campaign brings surges of traffic, causing your website or app to slow down and even crash. There’s nothing more heartbreaking than seeing your website or app fail just when you have the most to gain.

Most blogs and articles just state traffic-induced crashes as something that can happen. But if you don’t understand how high traffic crashes a website or app, how can you expect to avoid the problem?

Here’s what you’re overlooking:

You lack resources

The main reason websites and apps continue to slow down and, ultimately, crash under load is the disparity between traffic levels and the capacity of your website’s infrastructure.

The system requests made by your customers on your website overshadow its processing capacity resources and any third-party systems involved in the customer journey.

As a result, your website performance suffers.

Your website has bottlenecks

Not all requests made by your customers are equal. Some are more complex or demanding than others. This is why thinking of capacity only in terms of concurrent users just doesn’t cut it.

Imagine you’re at your local supermarket, which has room for many shoppers if they’re spread throughout the store. The main bottleneck exists at the checkout counters, served by several cashiers. But with only a handful of customers buying groceries, cashiers can keep the lines moving and the shoppers happy.

Suddenly, there’s a mad dash for the checkout counters. The number of shoppers in the store hasn’t changed. The cashiers are now overwhelmed and you’re feeling disgruntled. A lose-lose situation for everyone involved.

Like the throngs of shoppers all racing for the checkout counters, high online traffic puts pressure on bottlenecks in the system. It is these weak links that serve as limiting factors on website capacity.

You face unpredicted traffic surges

Let’s look at an example of the steps behind a website crash using one of the British Royal Family’s newest members.

Meghan Markle, the Duchess of Sussex, has a knack for causing websites to fail. She has a devoted group of followers who pay close attention to everything she wears. Her fashion choices crashed an online retailer’s site twice in 2018. It’s known as the Meghan Effect.

Let’s look at a customer journey for Meghan Markle’s latest outfit and the behind-the-scenes legwork the site’s database is doing.


Customer action



Sees Tweet about dress, clicks on link to designer’s home page

Loads images and browser script


Types name of dress into search bar

Complex search function must find all items that match search term(s), accounting for misspellings, product categories, and features, etc.


Browses list of products from search and clicks the dress

Loads images and browser script. Shows up-to-date inventory information.


Adds dress to cart

Inventory system must update to avoid overpurchasing and stay fully in sync for all other users


Proceeds to purchase by creating guest account

Sync dynamically entered information with membership database


Enter shipping information

Send and receive requests from shipping plugins, like address verification and shipping costs calculator


Enter payment information

Send dynamically entered information to payment gateway and awaits confirmation


Sees order confirmation

Inventory system updates stock remaining

Each step in the customer journey adds further pressure on the site’s infrastructure. Bottlenecks begin to appear where processing power is fully extended, and additional requests cannot be served.

Website visitors will experience this in the form of a website slowdown and eventual crash. So much for getting the royal treatment.

(Find a more technical discussion from a developer’s perspective here).

When does high traffic crash a website?

There are three major scenarios when high traffic can crash your website or app.

First: the unexpected traffic spike. This surge can occur because of the Meghan Effect, bot traffic, or an overly successful marketing campaign your website was not prepared for.


Figure 1. When your email newsletter campaign is an unexpected hit. (Source)

Second: big name sales like Black Friday and Singles’ Day. They can drive traffic levels 30 times higher than a normal day. But even with specific start-time events, the timing and level of online traffic spikes can be hard to predict.


Figure 2. A customer using Queue-it's virtual waiting room experienced several peaks of end-users in queue per minute during Black Friday.

Third: collection releases or campaigns when a limited quantity of products are made available. Releases can draw eager buyers to your website before the products drop. This opens the possibility that your site will crash before the sale even begins.

What can I do to prevent website crashes?

Don’t despair: website failure doesn’t have to be an unavoidable part of running overly successful campaigns.

Here are three questions you should ask yourself to minimize the risk of high online traffic crashing your site.

1. Have you optimized your website’s performance?

Identify heavy database requests on your website, and limit the number, size, and complexity of those requests. There are many ways to build performance into your website.

Use a content distribution network (CDN) to free up your servers to focus on dynamic content. Compress images and upload them at their intended display size. Minimize the use of plugins where possible.

2. Have you done load testing?

Load testing is one of the best preparations you can make for web traffic peaks. The aim is to help you understand how your website will perform when visitors hit it in big numbers.

Remember to set aside adequate time for load testing, as each test will reveal new bottlenecks that need fixing. At the same time, while it’s important to get started early, it also doesn’t make sense to test before the customer journey is complete.

Further, be sure to notify your hosting provider that you’re load testing. Many providers consider an unauthorized load test a violation of terms of service.

3. Where do your website’s excess users go?

In order to safeguard your website during traffic surges, you can choose to redirect excess users to an online queue. This has the benefit of managing traffic inflow along the whole user journey, keeping visitor levels where your website or app performs best.

A queue takes the heat off bottlenecks in your own infrastructure, as well as third-party integrations like payment gateways that have capacity limitations outside of your control.

Learn more about how a virtual waiting room protects your website during your business-critical events. 

There will also be a session on preparing for peak at the Eggplanet event in London on 6 June.

Topics:Customer ExperienceLoad testingPerformance testingintelligent automationecommerceRetail

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