Batch Auctions

Strike uses Frequency Batch Auctions (FBA) instead of continuous order matching. This is the core mechanism that determines how trades execute.

How a Batch Clears

1. Accumulate orders — during the batch interval (~3s), traders place and cancel orders. Orders are recorded on-chain but not matched yet.

2. Trigger clearing — anyone (typically a keeper) calls clearBatch(). This is permissionless.

3. Find clearing price — the contract traverses the segment tree to find the tick that maximizes matched volume:

   • Cumulative bid volume is computed descending from tick 99

   • Cumulative ask volume is computed ascending from tick 1

   • The clearing tick is where these curves cross

   • Tie-break: midpoint of tied ticks

4. Calculate fill fractions — at the clearing tick, one side may be oversubscribed. The fill fraction (in BPS) is stored for that side.

5. Store result — a BatchResult is written: clearing tick, fill fractions, total volume, batch ID. No per-order writes happen here — this is what keeps clearing gas-efficient.

6. Traders claim — after clearing, traders call claimFills() to receive their outcome tokens or collateral based on the batch result.

Fill Logic

Order Position	Result
Bid above clearing tick	Fully filled
Ask below clearing tick	Fully filled
At clearing tick (non-oversubscribed side)	Fully filled
At clearing tick (oversubscribed side)	Partially filled (pro-rata)
Bid below clearing tick	Not filled (remains resting)
Ask above clearing tick	Not filled (remains resting)

Why Batches?

vs. Continuous Matching

• No speed advantage — all orders in a batch are equal, eliminating latency races

• Uniform price — everyone gets the same price, not a sequence of price-moving fills

• Maker-friendly — makers have the full batch interval to cancel stale quotes

vs. Parimutuel Pools

• Real price discovery — prices are set by supply and demand, not pool ratios

• Capital efficient — traders can express precise views at specific prices

• Secondary market — outcome tokens are tradeable on the book, not locked until resolution

Batch Cadence

Setting	Duration	Best For
Multi-block (default)	~3s	Standard markets — balances fairness and UX
Long interval	10–30s	Low-volume markets, mobile-first UX

The batch interval is configurable per market at creation time.

Segment Tree

Clearing requires knowing cumulative volume at each tick. A naive approach iterates all 99 ticks — expensive on-chain. Strike uses a segment tree (inspired by Clober's LOBSTER research) to compute prefix sums and find the clearing tick in O(log N) operations with minimal storage writes.