I open-sourced the math, not the repo: how cumulative ranking + outbid-diff works
@sushantkr49Sep 18, 20268 min read
What is cumulative ranking?
Rank is not a vote, a like count, or an editorial pick. Rank is strictly ordered by cumulative money paid for each listing. If listing A has $210 in total bids and listing B has $205, A ranks higher. Full stop.
Cumulative (not latest-bid) matters because it makes every past payment load-bearing: you can't erase a rival's history, you can only outspend it. That single property is what turns one-time payments into bidding wars.
How do the outbid increments work?
Three numbers run the whole economy. The floor bid ($5 default) is the minimum to enter the board. The throne increment ($5) is the minimum gap required to take #1 — so a leader at $200 falls only to a $205+ bid. The standard increment ($1) covers every other rank.
The $5 throne rule exists to stop penny-sniping at the top: dethroning the most visible spot should cost a decision, not a reflex. The $1 rule elsewhere keeps the rest of the board in permanent, cheap motion.
What happens when you rebid the same URL?
Rebids add to your cumulative total — you only ever pay the difference. Holding #3 at $60 and wanting #1 at $205 costs $145, not $205. Your listing, history, and SEO page stay intact; only the total (and therefore the rank) moves.
This is the repeat-revenue engine: defending a rank is always cheaper than taking one, so holders keep topping up instead of churning.
How are ties broken?
First to reach the total holds the higher rank. If two listings sit at $100, whoever's bids summed to $100 first stays on top. Deterministic, explainable, and impossible to game after the fact — timestamp ordering is recorded at settlement time.
Why must bids settle atomically?
Because money plus concurrency is where hobby code dies. Two $205 bids landing in the same millisecond must resolve to exactly one winner and exactly one charge — never a double-spend, never a lost outbid, never two listings at #1.
The correct implementation settles each bid inside a single database transaction: lock the listing row, compute the new total, verify it beats the target rank, record the payment, commit. Anything outside the transaction (webhooks, tickers, confetti) reads from committed state only. This is the piece weekend clones skip — and the piece buyers never forgive you for skipping.
Quick answers
What are the default bid increments?
$5 floor to enter, $5+ over the leader to take #1, $1+ over any other rank. All three are one-line config changes per niche.
Do rebids cost the full rank price?
No — only the difference between your current total and the target. Same URL, same listing, same history; you pay the gap.
What stops two people claiming #1 at once?
Atomic settlement: each bid locks, verifies, records, and commits in one database transaction, so concurrent bids serialize into exactly one winner.
Ship this mechanic on your domain.
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