How we know
above 90-day avg classifierHow we observe prices
We read each product page directly on a fixed cadence — hot tier every 6 hours, daily tier every 24 hours. Smart-spread sharding distributes requests so we never hit Olive Young's servers in a burst. Every observation is stored with server time, DOM hash, and a subset of response headers.
Integrity (Merkle + TSA anchoring)
Each day we hash every observation into a Merkle tree and anchor the root to the freetsa.org RFC 3161 Time-Stamp Authority. Anyone can later verify cryptographically whether we tampered with historical price data after the fact.
The above 90-day avg classifier
Answers the simple question: "did the list price suddenly jump right before the sale?" Specific rules:
- List price rose ≥15% above 30-day median within 7 days before the sale started
- That list-price jump is NOT seen on the same SKU at other merchants (e.g. Naver)
- Both conditions → display the
above 90-day avgbadge
The classifier is a heuristic and can mislabel. To appeal a classification, email hello@glowmeter.beauty with the SKU link.
What data we store
- Observations: product ID, price, timestamp, DOM hash, response-header subset
- Derived: 30-day low, average, savings percentage
- What we do NOT store: visitor IPs, cookies, accounts (there is no signup)
The at 90-day low classifier
Current price is within 2% of the 90-day observed low → tagged at 90-day low. Represents a genuine floor-price event.
The below 90-day avg classifier
list_price higher than sale_price AND sale_price below 90-day average → below 90-day avg. Normal-tier discount.
What we publish
The methodology is public. This page is the whole of it — the formula, baseline window and threshold behind every at 90-day low / below 90-day avg / above 90-day avg label. Every SKU page shows its observation count and first-seen date, so you can check the price history we display against what you see on the retailer's own page.
The crawler source stays private. Publishing collection code means publishing a working anti-bot bypass, which helps nobody. We are not going to promise a future release date — we only write down things we can actually keep.