Ignite Live Blog: Get an overview of Microsoft Teams architecture

Published Sep 26 2017 10:12 AM 6,441 Views

Microsoft Teams is big, a lot bigger than you think. While it all comes together in a unified app hub experience there is an immense amount of integration and services behind the scenes that delivers the single application windows experience.

And that is something users need to remember – the Teams application provides a single desktop, mobile and web experience that sits on top of the collective Office 365 experience.


Teams builds on the top of key platform services such as Azure Active Directory, Skype for Business, SharePoint Online, with Azure powering everything in between.


In this session Dan Massey and Mark Longton explain in real terms the architecture that powers this app hub experience. The starting message here is that Teams is build for the cloud, provides agility with scalability, and amplifies the value of Office 365 by surfacing the most common experiences through the Teams client.


Dan called out how important it was that Teams talks directly to the services instead of simply being a API layer on top of the others.



Dan & Mark covered a number of topics giving insight into the sheer amount of services and development that goes into delivering the Teams experience.


Teams client architecture

  • Using multiple software development languages: Electron, C++, Objective C, HTML5/CC, Angular, jQuery, TypeScript, Node, SASS, C#, Swift, Java and others.

The importance of this is that it provides a unified experience across mobile, desktop and web – regardless of browser, operating system or mobile platform.


Teams services

Dan took us through the services that Teams owns, as opposed to other platform services they leverage. There are a number of front-end servers, as well as what is referred to as the “middle-tier” that cover identity, compliance, notifications, Team management, extensibility, and configuration. This “middle-tier” is a collection of micro services that is more efficient while reducing complexity, allowing for flexibility of scale, while also lowering risk and therefore increasing deployment agility.

Dan called out the importance of fact that this is only really achievable due to cloud services, whereas on-premises it would require an unimaginable amount of server infrastructure.


Teams and Skype

  • Leveraging next-generation Skype for Business services for messaging, VoIP calling, PSTN conferencing and calling


Teams and Office 365

  • Office 365 platform integrations with Office 365 Groups, Exchange, SharePoint Stream, OneDrive for Business, Information Protection, OneNote, PowerApps, Planner, PowerPoint/Word/Excel, and Power BI

Dan stressed the importance of not wanting to build any services that exist in Office 365 already, so as to leverage the best of breed experiences that are already available.

This highlights the point that Teams is the app hub.

Dan also spoke about the amount of signalling back and forth between Teams and the rest of Office 365, such as sending you an email when you haven’t been signed into Teams for more than 60-90 minutes and have notifications, creating Office 365 Groups when a new Team team is created, or removing chat messages due to Information Protection policies.


Teams on Azure

  • A whole lot of Azure services: Cloud Services, Storage, App Service, Media Services, Traffic Manager, Security Center, Azure Active Directory, Multi-Factor Authentication, Azure Active Directory B2B, Key Vault, Redis Cache, HockeyApp, Application Insights, Event Hubs, and Notification Hubs


High level architecture

Dan then took us through the signalling between Teams, Office 365 and Azure. He explained where micro-services might exist between two Azure or Office 365 services because Teams might want to perform some additional operations before handing over the information.


Regional partitioning

Mark took the stage at this point to talk about where Teams actually lives in the world.

At present Teams only exists in the three key regions: US, EMEA and APAC.

While chat data is stored in region base on tenant affinity, files are stored in the country that the tenant is billed in (where a datacentre is available). There are currently efforts to bring chat to country-based datacentres as well.



Mark called out that they are also working on making Teams available in US Federal Government environments too.


AAD Sync

At present most sync events are supported, however Group soft-delete & restore is not but is being worked on.


Conversation storage

The chat service operates in memory for speed, but leverages Azure storage. Messages are stored in Exchange for information protection, and conversation images are stored in Azure image storage.


File storage

Files are uploaded to either OneDrive or SharePoint depending on the audience of the conversation (eg. 1:N chat, or channel-based respectively)

Teams also supports some third-party storage providers – and obviously the files live there if so chosen.


Teams & Information Protection

To enable Information Protection Teams leverages the same services and user experiences that Exchange and SharePoint use. To do this Teams ingests all 1:N chats into individual mailboxes and team conversations into group mailboxes. At present the Information Protection features only work when the mailbox is online (it will not work when the mailbox is on-premises).


Teams guest access architecture

Guest access is built on Azure Active Directory B2B which means it can be managed through Teams, Office 365 Groups, SharePoint, Planner, other apps that provide group membership management, and obviously from within Azure Active Directory itself.


Teams outside of Office 365

Microsoft Teams doesn't support SharePoint on-premises: SharePoint Online is required to share and store files in team conversations. OneDrive for Business is required to share and store files in private chats.

If users aren't assigned and enabled with SharePoint Online licenses, they don't have OneDrive for Business storage in Office 365. File sharing will continue to work in Channels, but users are unable to share files in Chats without OneDrive for Business storage in Office 365.

Users must be enabled for Office 365 Group creation to create teams in Microsoft Teams.

In Microsoft Teams, security and compliance features like eDiscovery, Content Search, archiving, and legal hold work best in Exchange Online and SharePoint Online environments. For channel conversations, messages are journaled to the group mailbox in Exchange Online, where they're available for eDiscovery. If SharePoint Online and OneDrive for Business (using work or school account) are enabled across the organization and for users, these compliance features are available for all files within Teams as well.

While Teams can work with Exchange environments outside of Exchange Online multi-tenant, there are some restrictions.


Q & A

There were a number of questions about Skype for Business and Teams feature parity. Mark and Dan were clear in saying that it comes down to priority, not a choice of yes or not.

Dan called out that a big part of the success of Teams will come down the amount of control they can give to IT (in terms of restricting or disabling features).

Someone asked if OneDrive could be replaced with a third-party storage provider when using 1:N Chats, the answer was no.

In the scenario of tenant migrations, at present this is not supported but the Teams team are working with Exchange and Azure Active Directory teams on being able to deliver that.

Both sides of messages in 1:N chats are stored in the initiator’s mailbox, whereas the guest side is stored in the chat storage within Teams.

Similar to Skype for Business, if someone within Teams calls another person it is peer to peer. And like Skype for Business if another person joins it then becomes a meeting and goes via the cloud.

Dan and Mark.jpg 


I was not able to capture all the questions, but have also excluded questions from those from people who were unfamiliar with existing & documented functionality, the roadmap our out of the scope of infrastructure (eg. meetings & calling, specific Skype for Business transition scenarios, contact centres, etc.). There were also a number of feature wish-list styled questions, in that people were asking if a particular feature was coming in the future which was obviously something they would like to see themselves.



Dan and Mark did a fantastic job of explaining what goes on underneath the application layer of Teams and answering a while raft of questions across a whole range of different topics – including those that weren’t on topic. The recording of the session will be online soon from https://www.microsoft.com/en-us/ignite

Keep following the news and have a conversation with me about Microsoft Teams on Twitter as @LoryanStrant or my blog www.loryanstrant.com.

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