Caching Cookies and Personalised Content
Caching is what makes pages fast, but personalisation — showing a visitor their name, basket or recommendations — is what makes them relevant. These two goals pull in opposite directions, because a cached page is the same for everyone.
The art is in caching everything that is safe to share while keeping each visitor's personal content accurate.
The Balance We Aim For
The target is to keep the speed benefits of caching while showing every visitor their own correct, current information. With the right structure, you rarely have to sacrifice one for the other.
- Cache the heavy, shared parts of each page.
- Load personal details separately and freshly.
- Vary the cache where visitors differ.
- Keep sensitive content out of any shared cache.
Why Getting It Wrong Is Risky
Mishandling cached personalised content is not just a performance issue — it can be a privacy one. If a cached page containing one person's details is shown to another, that is a serious problem, so we treat this carefully.
- Never cache pages showing names, baskets or account details for sharing.
- Separate the shared layout from the personal content.
- Use cookies to vary the cache where appropriate.
- Test thoroughly with multiple accounts before going live.
The Conflict
If you cache a page that contains someone's name or basket, another visitor could be served that personal content. So personalised pages are often excluded from caching entirely — which makes them slower.
How We Balance Both
- Cache the shared parts of the page and load personal bits separately.
- Vary the cache by relevant cookies so logged-in and logged-out visitors get the right version.
- Fetch personalised fragments after the main page loads.
- Keep truly sensitive areas out of any shared cache.
Frequently Asked Questions
Can a personalised site still be fast?
Yes. By caching the heavy shared parts and loading personal details separately, we get most of the speed benefit without showing the wrong data.
If you need a hand with any of this, your Progressive Robot delivery team is ready to help. Raise a ticket from the Support area of your client portal or speak to your account manager and we will guide you through the next steps.