Web applications need databases for storing and serving information. But not all databases are created equal — oh, no, far from it. The popularity of any particular database — be it SQL, NoSQL, key-value, or graph — waxes and wanes, and really, it depends who you ask.

Among developers who use Amazon Web Services — the biggest public cloud going today — some are more much widely used than others.

Redis Labs, a startup that provides versions of the Redis and Memcached databases on the Amazon, Google, IBM, and Microsoft public clouds, took some time out to speak with 126 developers in attendance at Amazon’s re:Invent user conference in Las Vegas last month and came away with some fascinating findings.

For instance, almost half of the developers surveyed said they used the MongoDB open-source NoSQL database.

NoSQL databases

Above: NoSQL databases

Image Credit: Redis Labs

Memcached and Redis weren’t very far behind, with both coming in between 30 and 40 percent.

Relational databases, meanwhile, still have their place in development stacks. MySQL — the M in LAMP — lead the pack with more than 70 percent of developers surveyed saying they use it.

SQL databases used on Amazon Web Services

Above: SQL databases used on Amazon Web Services

Image Credit: Redis Labs

Microsoft’s SQL Server came in No. 2, with PostgreSQL picking up the No. 3 spot.

The surveyors also asked developers about their biggest challenges with databases. Performance was the most popular answer, followed by scalability.

Database challenges

Above: Database challenges

Image Credit: Redis Labs

Performance is the biggest reason developers choose Redis, Cameron Peron, Redis Labs’ vice president of marketing, noted in a blog post that the startup was planning to publish alongside these results.