@Override
  public Call<List<Span>> getTrace(String traceId) {
    // make sure we have a 16 or 32 character trace ID
    traceId = Span.normalizeTraceId(traceId);

    // Unless we are strict, truncate the trace ID to 64bit (encoded as 16 characters)
    if (!strictTraceId && traceId.length() == 32) traceId = traceId.substring(16);

    SearchRequest request = SearchRequest.create(asList(allSpanIndices)).term("traceId", traceId);
    return search.newCall(request, BodyConverters.SPANS);
  }
To not produce unnecessarily long queries, we don't look back further than first ES support
zipkin-storage/elasticsearch/src/main/java/zipkin2/elasticsearch/ElasticsearchSpanStore.java