On March 4, 2010 I saw an email from our CEO, Steve Ballmer, in my inbox. I don't normally receive much email from him, so I gave it my full attention. The subject line of the email was: "We are all in," and it summarized the commitment of Microsoft to cloud computing. If I needed another confirmation of what I already knew, that Microsoft is serious about the cloud, there it was.

My first contact with what eventually became Windows Azure, and other components of what is now called the Windows Azure platform, was several years ago. I was in the Developer & Platform Evangelism (DPE) team, and my job was to explore the world of software delivered as a service. Some of you might even remember a very early mockup I developed in late 2007, called Northwind Hosting. It demonstrated many of the capabilities that the Windows Azure platform offers today. (Watching an initiative I've been involved with since the early days become a reality makes me very, very happy.)

In February 2009, I left DPE and joined the patterns & practices team. My mission was to lead the “cloud program” - a collection of projects that examined the design challenges of building applications for the cloud. When the Windows Azure platform was announced, demand for guidance about it skyrocketed.

As we examined different application development scenarios, it became quite clear that identity management is something you must get right before you can consider anything else. It's especially important if you are a company with a large portfolio of on-premises investments, and you want to move some of those assets to the cloud. This describes many of our customers.

In December 2009, we released the first edition of A Guide to Claims-Based identity and Access Control. This was patterns & practices's first deliverable, and an important milestone in our cloud program. We followed it with Moving Applications to the Cloud. This was the first in a three part series of guides that address development in Windows Azure. Both of these guides have been regularly updated as Windows Azure evolves.

Windows Azure is special in many ways. One is the rate of innovation. The various teams that deliver all of the platform's systems proved that they could rapidly ship new functionality. To keep up with them, I felt we had to develop content very quickly. We decided to run our projects in two-months sprints, each one focused on a specific set of considerations.

This guide covers a Greenfield scenario: designing and developing new multi-tenant applications for the Windows Azure platform. This follows on from the previous guide that focused on how to move an existing application to the Windows Azure platform. As in the previous guides, we've developed a fictitious case study that explains, step by step, the challenges our customers are likely to encounter.

I want to start by thanking the following subject matter experts and contributors to this guide: Dominic Betts (Content Master Ltd), Scott Densmore (Microsoft Corporation), Ryan Dunn, Steve Marx, and Matias Woloski. Dominic has the unusual skill of knowing a subject in great detail and of finding a way to explain it to the rest of us that is precise, complete, and yet simple to understand. Scott brought us a wealth of knowledge about how to build scalable Windows Azure applications, which is what he did before he joined my team. He also brings years of experience about how to build frameworks and tools for developers. I've had the privilege of working with Ryan in previous projects, and I've always benefited from his acuity, insights, and experience. As a Windows Azure evangelist, he's been able to show us what customers with very real requirements need. Steve is a technical strategist for Windows Azure. He's been instrumental in shaping this guide. We rely on him to show us not just what the platform can do today but how it will evolve. This is important because we want to provide guidance today that is aligned with longer-term goals. Last but not least, Matias is a veteran of many projects with me. He's been involved with Windows Azure since the very first day, and his efforts have been invaluable in creating this guide.

As it happens with all our written content, we have sample code for most of the chapters. They demonstrate what we talk about in the guide. Many thanks to the project's development and test teams for providing a good balance of technically sound, focused and simple-to-understand code: Masashi Narumoto (Microsoft Corporation), Scott Densmore (Microsoft Corporation), Federico Boerr (Southworks), Adrián Menegatti (Southworks), Hanz Zhang (Microsoft Corporation), Ravindra Mahendravarman (Infosys Ltd.), Rathi Velusamy (Infosys Ltd.).

Our guides must not only be technically accurate but also entertaining and interesting to read. This is no simple task, and I want to thank Dominic Betts (Content Master Ltd), RoAnn Corbisier (Microsoft Corporation), Alex Homer (Microsoft Corporation), and Tina Burden from the writing and editing team for excelling at this.

The visual design concept used for this guide was originally developed by Roberta Leibovitz and Colin Campbell (Modeled Computation LLC) for A Guide toClaims-Based Identity and Access Control. Based on the excellent responses we received, we decided to reuse it for this guide. The guide design was created by John Hubbard (eson). The cartoon faces were drawn by the award-winning Seattle-based cartoonist Ellen Forney. The technical illustrations were adapted from my Tablet PC mockups by Rob Nance and Katie Niemer.

All of our guides are reviewed, commented upon, scrutinized, and criticized by a large number of customers, partners, and colleagues. We also received feedback from the larger community through our CodePlex website. The Windows Azure platform is broad and spans many disciplines. We were very fortunate to have the intellectual power of a very diverse and skillful group of readers available to us.

I also want to thank all of these people who volunteered their time and expertise on our early content and drafts. Among them, I want to mention the exceptional contributions of David Aiken (Microsoft Corporation), Graham Astor (Avanade), Edward Bakker (Inter Access), Vivek Bhatnagar (Microsoft Corporation), Patrick Butler Monterde (Microsoft Corporation), Shy Cohen, James Conard (Microsoft Corporation), Brian Davis (Longscale), Aashish Dhamdhere (Windows Azure, Microsoft Corporation), Andreas Erben (DAENET), Giles Frith, Eric L. Golpe (Microsoft Corporation), Johnny Halife (Southworks), Simon Ince (Microsoft Corporation), Joshy Joseph (Microsoft Corporation), Andrew Kimball, Milinda Kotelawele (Longscale), Mark Kottke (Microsoft Corporation), Chris Lowndes (Avanade), Dianne O'Brien (Windows Azure, Microsoft Corporation), Steffen Vorein (Avanade), Michael Wood (Strategic Data Systems).

I hope you find this guide useful!

Eugenio Pace

Senior Program Manager – patterns & practices

Microsoft Corporation

Acknowledgements of Contributors to the Third Edition

Windows Azure is an evolving platform. We originally published the first edition of this guide in 2010, demonstrating a basic set of Windows Azure features. I’m now pleased to release the third edition of this guide, which is more tailored to multi-tenant scenario. This new edition describes common challenges in the multi-tenant Software as a Service applications such as partitioning data, data extensibility, automated provisioning, customizing to multiple tenants, and so on.

As our scope increased, we also added new community members and industry experts who have provided significant help throughout the development of this edition. I want to acknowledge the exceptional contributions of following people: Dominic Betts (ContentMaster), Alex Homer (Microsoft Corporation), Alejandro Jezierski (Southworks), Mauro Krikorian (Southworks), Jorge Rowies (Southworks), Marcos Castany (Southworks), Hanz Zhang (Microsoft Corporation), Rathi Velusamy (Infosys), RoAnn Corbisier (Microsoft Corporation), Nelly Delgado (Microsoft Corporation), Eugenio Pace (Microsoft Corporation), Carlos Farre (Microsoft Corporation), Trent Swanson (Full Scale 180 Inc.), Ercenk Keresteci (Full Scale 180 Inc.), Jane Sinyagina (Microsoft Corporation), Hatay Tuna (Microsoft Corporation), Patrick Butler Monterde (Microsoft Corporation), and Michael Wood. I also want to thank everyone who participated in our CodePlex community site.

Masashi Narumoto

Senior Program Manager – patterns & practices

Microsoft Corporation

Redmond, October 2012