MongoDB's NoSQL document store has now overtaken PostgreSQL for popularity, landing in the fourth slot in db-engines.com's database engine popularity ranking. MongoDB is the only NoSQL engine in the top five on the site for August 2015; previously, MongoDB was number five on the list.
Also rising are Cassandra and Redis. Cassandra gained the number eight spot (previously being number ten) while Redis was bumped to the top ten from its eleventh place. SQLite and SAP Adaptive Server fell to the ninth and eleventh spots, respectively.
DB-Engines Ranking is based on a variety of factors that are updated throughout the month. Such factors include:
Number of "mentions" of the database on other websites uses metrics from Google and Bing.
General interest, i.e. Google Trends statistics.
Frequency of "technical discussions" per Stack Overflow and DBA Stack Exchange.
Number of job offers in which the database is listed as a requirement via job search engines.
Number of professional profiles on sites such as LinkedIn that mention the database.
Number of Tweets mentioning the database.
DB-Engines Ranking clarifies that they do not take installations or IT system use into account.
The site is significant as it acts as a unbiased predictor of what databases will find success in the industry. The current top ten list of engines is as follows: