Many data processing tasks can be thought as small mutations to a large database triggered by events. Contrary to batch processing, the incremental processing model achieves very low delay from the reception of an event to the application of the mutation. In the absence of transactions support, developers have to use ad-hoc mechanisms to ensure atomic execution of mutations despite failures and concurrent accesses to the database by other clients. Most NoSQL data stores, like HBase, BigTable and Cassandra, lack support of transactions, which makes them unsuitable for a whole range of applications. In this talk we present Omid, an open source tool for transactional support and incremental processing on top of HBase (https://github.com/yahoo/omid). Due to the centralized nature of its client-replicated status oracle, Omid (i) avoids distributed locks, (ii) scales up to 60,000 TPS and a thousand clients, (iii) requires no changes to HBase, and (vi) adds a negligible overhead to data servers.