Latest Posts


NoSQL databases are often compared by various non-functional criteria, such as scalability, performance, and consistency. This aspect of NoSQL is well-studied both in practice and theory because specific non-functional properties are often the main justification for NoSQL usage and fundamental results on distributed systems like the CAP theorem apply well to NoSQL systems.  At the same time, NoSQL […]


Java was initially designed as a safe, managed environment. Nevertheless, Java HotSpot VM contains a “backdoor” that provides a number of low-level operations to manipulate memory and threads directly. This backdoor – sun.misc.Unsafe – is widely used by JDK itself in the packages like java.nio or java.util.concurrent. It is hard to imagine a Java developer who uses this backdoor in […]


In this article I digested a number of MapReduce patterns and algorithms to give a systematic view of the different techniques that can be found on the web or scientific articles. Several practical case studies are also provided. All descriptions and code snippets use the standard Hadoop’s MapReduce model with Mappers, Reduces, Combiners, Partitioners, and sorting. This […]


ACID transactions are one of the most widely used software engineering techniques, a cornerstone of  the relational databases, and an integral part of the enterprise middleware where transactions are often offered as the black-box primitives. Notwithstanding all these and many other cases, the old-fashion approach to transactions cannot be maintained in a variety of modern large […]

This post is a second part of Ultimate Sets and Maps for Java. In the first part, we discussed memory-efficient implementations of sets and maps. These data structures efficiently support contains(key) operation. In this part of the article, we discuss more advanced querying: How to efficiently test that a collection of items meets a filtering criteria contains(key1) AND contains(key2) […]