The most painful site crash never happens in the middle of the night when nobody is around. It happens the instant you launch an ad campaign or announce a sale and hundreds of people land on the page at once. The ad budget is already spent, the buyers have already clicked — and the site is spinning an endless loader or showing an error. Within minutes half of those people leave and never come back.

The frustrating part is that this can almost always be foreseen. A traffic spike is not a natural disaster — it’s a scheduled event. You know the date of the sale yourself, and you have a rough idea of how many people the ad will bring. Which means you can prepare for it. We’ve run our studio since 2018 and support sites that go through these surges regularly, so here, in plain terms, is what to do in advance and what to keep on hand during the day itself.

One thing matters most: a site doesn’t survive “a lot of people in general” — it survives a specific number of simultaneous visitors. On an ordinary day that’s a few dozen; during a sale it can be dozens of times more. It’s that jump, not the daily total, that decides whether the site holds or falls.

Why sites crash exactly at the peak

Picture a checkout in a shop. On a normal day a queue of two people clears instantly. But if a hundred walk up to a single register at once, people start waiting, the line stretches, and some give up and leave. A website works much the same way: every request takes a sliver of capacity, and while there are few of them everything flies. When their number suddenly multiplies, capacity runs out, requests start waiting on one another — and at some point the site simply can’t keep up with answering.

The usual culprits are a handful:

  • The site was never built for the jump. It handles everyday traffic calmly, but nobody ever checked what happens under ten or twenty times that load.
  • One bottleneck slows everything. Most often it’s heavy pages rebuilt from scratch each time, or an overloaded database that everyone hits at once.
  • There’s no headroom. The site runs on exactly the capacity that’s enough on a normal day, with zero reserve for a surge.

What to check in advance, before the sale

The real work happens not on peak day but a week or two before it, while there’s still time to fix things calmly.

  • Load-test the site ahead of time. This is the big one. You artificially simulate a crowd arriving — and it becomes clear at what number the site starts to choke and exactly what slows it down. Without this test, you’ll learn the limit on live buyers.
  • Speed up the heavy pages. The homepage, the catalog and the sale page should be served ready-made, not rebuilt for every visitor. A ready page costs the site almost nothing to hand out, and that’s what saves you most during a peak.
  • Offload images and heavy files. Banners and sale photos should be compressed as much as possible and served so they don’t eat into the main site’s capacity.
  • Add a capacity reserve for these days. For the sale period it’s sensible to temporarily give the site more resources, then scale back afterward — so you’re not paying for excess year-round.
  • Trim the non-essentials during the peak. Various heavy extras that a purchase works fine without can be switched off for the duration of the sale, so they don’t steal strength from the main flow.

What to keep ready on peak day

Even a well-prepared site needs watching on sale day. A peak is not a “launch it and go for coffee” situation.

  • Watch the site with live eyes. You want monitoring that tells you immediately if the site starts slowing or throwing errors — not learning about a crash from angry customer messages.
  • Have a plan for overload. A short, honest queue that says “please wait a few seconds” beats a bare error page. A person who sees the site is alive and expecting them usually stays.
  • Don’t turn the whole campaign on at once if you’re unsure. Sometimes it’s wise to release the ads in waves rather than one blast, to see how the site reacts to a smaller stream and hedge your bets.
  • Keep someone reachable. During the hottest hours there should be a person nearby who understands the site and can react fast — not scramble to find a contractor on a Sunday evening.

After the peak: get ready for the next one

Once the wave subsides, don’t rush to forget it. It’s the most valuable material for next time. Look at the visitor count where the site started to strain, where exactly it lagged, how many people left without waiting. These numbers honestly tell you what to reinforce before the next campaign, and where the reserve was excessive and could be trimmed to save money. That way each peak passes more smoothly than the last.

If you have a sale or a big ad launch coming and you’re not sure the site will hold, don’t test that on live buyers. Write to us: we’ll load-test your site in advance, find the bottlenecks and prepare it for the peak — so that sale day brings sales, not lost customers and a ruined mood.