Thursday, November 11, 2010

SQL now, NoSQL later

This post is about trade-offs of choosing a NoSQL database vs. a traditional relational database specifically in the context of a new business or a start-up.

In the recent years there is more and more interest in NoSQL databases. One of the main motivations for using such databases is their ability to provide massive scale needed in large applications. Naturally biggest internet sites such as Facebook, Linked-in and the like are heavily using and even developing NoSQL solutions.

As with everything else in life there are always trade-offs. A famous triangle helps to visualize main competing forces when implementing a distributed system. People going for NoSQL solution are usually aware of the trade-offs and adjust their systems accordingly.

Less often mentioned is the lack of NoSQL tooling that has been developed for more traditional relational databases. Such tools include IDE support, code libraries, ORMs, entire CRUD generators and the reporting solutions. These tools significantly expedite development of new software. Just think of Rails' Active Record or Java's Hibernate.

This bring us to the main point: a new, possibly start-up company, is usually more concerned with getting the product out of the door as soon as possible and validating the business model than preparing for “inevitable” Facebook-like success.
Many successful companies tell the same story about iterating between various ideas and models before finally hitting a successful one. In such rapid iteration and evaluation - tools are crucial in providing the necessary productivity and speed. Using ready-made tools for relational databases, ideas can be prototyped, deployed and evaluated much faster than with custom made solutions.

Developers from Facebook and Linked-in emphasize that their initial solutions were the simplest ones possible. Linked-in used to run a relational DB for most of its data. Facebook used to host photos as separate files on a simple NFS. Only when they became successful they invested in scalable NoSQL solutions.

It is not an unreasonable approach therefore to start with the simplest relational DB (mysql?) and rapidly create a working product that can validate the business model. If the model is right, it will generate enough interest and money to evolve the solution with more scalable NoSQL DBs. If the idea is not successful, however, a lot less resources were spend on it and more resources and time can be spent on trying the next idea.

Main objection to this approach is that it requires throwing away a solution and re-creating it with NoSQL. While it’s true to some extent, it is not necessary to throw away all the code. In addition to that, usually after first release, there is enough new knowledge about the system and the business that a significant part of the code will change anyways.

In conclusion: while NoSQL solutions provide huge benefits for massively scalable applications, developing with NoSQL might not be the best option when trying a new business idea. Relational databases provide easier and faster route for experimentation and evolution of a business model.

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