Mosquito is a lightweight and adaptive physical design framework for Hadoop. Mosquito connects to existing data pipelines in Hadoop MapReduce and/or HDFS, observes the data, and creates better physical designs, i.e. indexes, as a byproduct. The authors' approach is minimally invasive, yet it allows users and developers to easily improve the runtime of Hadoop. They present three important use cases: first, how to create indexes as a byproduct of data uploads into HDFS; second, how to create indexes as a byproduct of map tasks; and third, how to execute map tasks as a byproduct of HDFS data uploads.