private OffsetSync lookupLatestSync(OffsetSync[] syncs, long upstreamOffset) {
        // linear search the syncs, effectively a binary search over the topic offsets
        // Search from latest to earliest to find the sync that gives the best accuracy
        for (int i = 0; i < SYNCS_PER_PARTITION; i++) {
            OffsetSync offsetSync = syncs[i];
            if (offsetSync.upstreamOffset() <= upstreamOffset) {
                return offsetSync;
            }
        }
        return syncs[SYNCS_PER_PARTITION - 1];
    }
Start the OffsetSyncStore, blocking until all previous Offset Syncs have been read from backing storage.
connect/mirror/src/main/java/org/apache/kafka/connect/mirror/OffsetSyncStore.java