static boolean hasClashOnLowerTraceId(List<List<Span>> input) {
    int traceCount = input.size();
    if (traceCount <= 1) return false;

    // NOTE: It is probably more efficient to do clever sorting and peeking here, but the call site
    // is query side, which is not in the critical path of user code. A set is much easier to grok.
    Set<String> traceIdLows = new LinkedHashSet<>();
    boolean clash = false;
    for (List<Span> spans : input) {
      String traceId = lowerTraceId(spans.get(0).traceId());
      if (!traceIdLows.add(traceId)) {
        clash = true;
        break;
      }
    }
    return clash;
  }
Returns true if any trace clashes on the right-most 16 characters of the trace ID
zipkin/src/main/java/zipkin2/storage/StrictTraceId.java