On Monday, the San Francisco-based company announced the opening of its Hamburg office in a blog post. This is part of a European expansion outlined in February, which also included a new Dropbox office in Amsterdam. The Hamburg site will support users in Austria, Germany, and Switzerland, forming a zone that will be led by former SAP Germany exec Oliver Blüher.

Dropbox already had international offices in Dublin, London, and Paris.

Dropbox is working with Amazon (AMZN) Web Services in Europe. While customer metadata will be kept on Dropbox equipment as part of the company’s recently disclosed “Magic Pocket” project, all files, documents, and other content will be stored on AWS.

For more, read: A Wild and Wooly Week in Cloud Computing

In tech speak, metadata is data about the data. A file’s metadata, for example, would include tidbits like who created the file, who accessed it, who made changes, who has rights to read it, and more. In a old world analogy, a book would be the data. But the author, date of publication, publishing house, and editor details would be the book’s metadata.

In March, Dropbox said it had moved 90% of its storage off of AWS onto its own specially-designed gear, but noted that it will continue to work with AWS outside the United States as it is doing now in Germany.

There’s good reason for that. In Europe—especially in Germany and Switzerland—there are strong data sovereignty rules mandating that their citizens’ data remain within the country of origin. AWS, which has been in the business of selling shared computing, storage, and networking resources for 10 years, runs a set of huge data center farms all over the world, including one that opened in Frankfurt two years ago.

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Data sovereignty concerns are one reason that Amazon, Microsoft (MSFT), IBM (IBM) and other cloud providers are building data centers around the world at a furious clip. Another reason is that to assure good performance, cloud data centers need to be as close to end users as possible. The longer the distance between the customer initiating an operation and the cloud computers that perform the operation, the longer the lag time or latency.

A Dropbox spokesman said the company will start offering AWS-backed Dropbox Business services to customers during the third quarter. Dropbox Business is the paid, business-focused product of the cloud company. Consumers can use Dropbox free up to 2GB of data.

This story was updated to correct number of users Dropbox claims. It is a half a billion, not a billion.