public CachingTableDescriptor<K, V> withReadTtl(Duration readTtl) {
    this.readTtl = readTtl;
    return this;
  }
Specify the TTL for each read access, ie. record is expired after
the TTL duration since last read access of each key.
@param readTtl read TTL
@return this descriptor
samza-api/src/main/java/org/apache/samza/table/descriptors/CachingTableDescriptor.java