Polymarket On-Chain Settlement Translation & Caching Gateway

1. Architectural Challenge

When auditing sports betting execution on-chain, the system queries the Polymarket CLOB client for past trade logs and compares them against settled conditions. This workflow historically suffered from three core engineering failures:

1. Strict String Comparison Mismatch: Polymarket CLOB trade logs return outcomes as the literal target asset names (e.g., "Washington Nationals" or "Hanwha Eagles"). However, the underlying on-chain sports markets resolve as binary condition contracts where the winner is resolved to indices in the outcomes array, while standard endpoints fall back to checking binary outcomes like ["Yes", "No"]. Direct comparisons of literal outcomes against settled winners failed (e.g., "Washington Nationals" === "Yes" evaluates to false), causing the engine to count winning trades as losses and flatline realized profits at 0.00. 2. Ignored Singular Routing Parameters: Querying Gamma API's /markets endpoint with singular parameters like condition_id= is ignored by the API design, causing the server to silently drop the query filter and return a default page of active markets (e.g. "New Rihanna Album before GTA VI?"). 3. Sequential Throttling Penalties: Sequential queries across1,000+historical trades hit rate-limiting blocks (429$) due to a lack of stateful caching, resulting in hang-ups and timeouts.

2. The Solution: PolymarketGateway

The gateway (PolymarketGateway.ts) is a stateful translation and query optimization layer:

• Plural query filtering: Gamma requests use repeated condition_ids parameters with an active/closed fallback (closed=true) so settled contracts resolve correctly.
• Semantic translation matrix: The gateway parses the outcomes array, resolves the winner from winningOutcomeIndex (or outcomePrices fallback), and compares that team name to the CLOB trade outcome string.
• Double-layer caching: Metadata is cached by conditionId across serverless instances to avoid redundant Gamma calls and rate-limit stalls.

3. Middleware Implementation

// Batch Gamma lookups — singular condition_id is ignored by the API
const params = new URLSearchParams();
for (const id of conditionIds) {
    params.append("condition_ids", id);
}
if (closed) params.set("closed", "true");

// Compare literal CLOB outcomes against resolved team names
for (const [outcome, size] of Object.entries(m.positions)) {
    if (size > 0.01 && outcome.trim().toLowerCase() === m.winner.trim().toLowerCase()) {
        payout += size * 1.0;
    }
}

// Baseball win rate uses the highest gross-buy side as the primary pick
if (m.isBaseballMoneyline && m.winner) {
    const primaryPick = this.getPrimaryPick(m);
    const pickUsd = primaryPick ? m.grossBuyUsd[primaryPick] || 0 : 0;
    if (primaryPick && pickUsd >= minPickUsd) {
        baseballResolvedMarkets++;
        if (primaryPick.trim().toLowerCase() === m.winner.trim().toLowerCase()) {
            baseballWinningPicks++;
        }
    }
}

Settlement math keys markets by conditionId and buckets MLB/KBO realized profit separately for portfolio-level audits.