MongoDB is known as a key-value document store, meaning it emphasizes quick data storage and retrieval.
It some cases, this approach is not a good fit.
MongoDB was a bad choice for powering the ill-fated open-source Diaspora social network, developer Sarah Mei has claimed.
That project needed a relational data store, in which some data needed to be permanently linked to other data. MongoDB was best suited for storing documents that don't need to be connected to one another in complex ways, Mei said.
In The Weather Channel's case, however, MongoDB proved to be a good fit. "Our data access patterns were actually matching the NoSQL model pretty well," Kolin said.
Weather forecasts for specific locations make up the vast majority of data the channel sends out. "Those access patterns suit themselves very well to key-value stores," Kolin said. The company doesn't have the vast Web of interconnected data that Diaspora had.
More importantly, if the structure of the data changes, then MongoDB's schema can be easily adjusted, something that can not be done so easily in a relational database and associated software.
"Every time there was a simple, trivial change, we were having to modify five or six different components at three or four different levels of the stack," Kolin said
MongoDB also brings The Weather Channel a much needed promptness.
The company has a set of alert services that send out warnings when severe weather is imminent. When a severe-weather warning is issued for a heavily populated area, such as Chicago, The Weather Channel must send alerts to the thousands of users who live in the affected ZIP codes, preferably within seconds.
The company tested a range of NoSQL databases, including Cassandra, Riak, CouchDB and MongoDB, as well as MySQL, to determine which one could most quickly filter a few thousand users from a much larger pool of candidates. MongoDB proved to be the best fit, able to deliver the information within seconds.
In addition to The Weather Channel, other companies that use MongoDB include MetLife, Bosch, Expedia, ADP and the city of Chicago.
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