Dropbox Inc. built the world’s most popular file sharing and storage service on the back of Amazon Web Service’s cloud infrastructure, but after years hosting its services in the cloud, it’s now using its own technology instead.

“We’re excited to announce that we’re now storing and serving over 90 percent of our users’ data on our custom-built infrastructure,” Dropbox VP of Engineering Akhil Gupta said in a blog post Monday.

Gupta revealed that Dropbox was one of the earliest adopters of Amazon’s S3 service to store bulk data, but that now its was handling more than 90 percent of its own storage needs.

“As the needs of our users and customers kept growing, we decided to invest seriously in building our own in-house storage system,” he said, adding that Dropbox has always used a hybrid architecture, with metadata and Web services kept in-house, and file content usually stored on Amazon’s cloud.

However, Dropbox’s massive growth prompted the company to begin building its own storage infrastructure back in 2013, and this was up and running by early 2015. Last October, Dropbox achieved its goal of shifting 90 percent of its data to its in-house infrastructure.

“We knew we’d be building one of only a handful of exabyte-scale storage systems in the world,” Gupta said. “It was clear to us from the beginning that we’d have to build everything from scratch, since there’s nothing in the open source community that’s proven to work reliably at our scale.”

Gupta says the advantages are twofold, because Dropbox can now boost performance by optimizing its in-house storage systems to eliminate the lag that comes with the public cloud. In addition, the company’s overheads can be reduced through hardware and software optimization of its storage needs.

As far as the performance gains go, these are pretty impressive. Gupta claims data durability of more than 99.9999999999 percent, while availability is over 99.99 percent. All data is encrypted at rest, and Dropbox will add additional infrastructure to speed things up even more.

More than anything else, Dropbox’s move highlights the argument for the private cloud when enterprises reach a certain scale. While some companies, such as Netflix Inc., have gone all-in on the AWS cloud, others have flitted back and forth. Games maker Zynga Inc. started out using its own infrastructure, shifted to the cloud, and is now in the process of moving to its own infrastructure again, showing that the grass isn’t always greener on the other side of the fence.

Dropbox’s own case suggests that its reached a scale at which its incremental costs will actually go down by moving away from a cloud provider. The only catch is it first has to build its own infrastructure and maintain it in order to achieve those savings. But if the company fails to scale as it plans, those cost savings may never materialize.

Image credit: Skeeze  via pixabay