<b>The retailer whose A/B test killed their cache</b>

<b>The retailer whose A/B test killed their cache</b>

A shoe retailer ran homepage A/B tests through a client-side script. It worked, but it forced the homepage to be uncacheable — the test logic needed a fresh server response to assign variants. Their highest-traffic page ran 100% origin, and Los Angeles users watched a 900ms blank flash before the variant painted.

We moved variant assignment to an edge function. The edge reads or sets the bucket cookie, then serves the matching variant — both fully cached at the edge, decided in under a millisecond at the point of presence.

The homepage went from 0% to 99% cache-hit. The LA variant-flash disappeared; the correct version paints on first render. Origin homepage requests dropped from 1.2M to 11k a day.

The number that mattered: homepage cache-hit 0% to 99%.