Real-Time MLS & RESO Web API Sync: High-Throughput Architecture for Brokerages

import { createODataClient } from "@reso/odata-client";
import { redisPublisher } from "@/lib/redis";

export async function pollMlsDeltas(lastSyncTimestamp: string) {
  const client = createODataClient({
    endpoint: process.env.RESO_API_URL!,
    token: process.env.RESO_BEARER_TOKEN!,
  });

  // Query only records modified since last timestamp
  const filter = `ModificationTimestamp gt ${lastSyncTimestamp}`;
  const stream = await client.getProperties({
    $filter: filter,
    $select: ["ListingKey", "StandardStatus", "ListPrice", "City", "Coordinates"],
    $top: 500,
  });

  for await (const listing of stream) {
    // Publish instantly to Redis channel for websocket dispatch
    await redisPublisher.publish("mls:listing:updated", JSON.stringify(listing));
  }
}