This document discusses blockchains and their relationship to the Internet of Things (IoT). It first provides background on Bitcoin and key aspects of blockchain technology like decentralization and immutability. It then explains how blockchains could make financial services faster, safer and cheaper compared to traditional centralized systems. The document outlines core blockchain design principles and how public and enterprise blockchains optimize scalability and consistency while remaining decentralized. It presents examples of implementing enterprise blockchains using a blockchain software stack with layers for applications, the blockchain, and an underlying database. The document argues that MongoDB is well-suited as the database layer due to its scalability, availability, data model flexibility, querying and secondary indexes.