How Microsoft 365 built a platform engineering layer on AKS to ship faster at global scale

Suma SaganeGowda

Microsoft

Jul 15, 2026

Microsoft’s Customer Zero blog series gives an insider view of how Microsoft builds and operates Microsoft using our trusted, enterprise-grade agentic platform. Learn best practices from our engineering teams with real-world lessons, architectural patterns, and operational strategies for pressure-tested solutions in building, operating, and scaling AI apps and agent fleets across the organization.

Challenge: Scaling success without increasing complexity 

Microsoft 365 runs a broad portfolio of services across global and sovereign clouds. At that scale, the platform has to do more than schedule workloads. It has to enforce security boundaries, meet enterprise compliance requirements, and support reliable change management across every service that runs on it.

Without a shared foundation, each service team ended up solving the same problems on its own: how to provision correctly, deploy safely, meet policy requirements, and stay resilient as traffic and complexity grew. That slowed teams down and produced unnecessary variation in how services were built and operated.

What Microsoft 365 needed was a hosting experience that could absorb operational complexity centrally so product teams could focus on customer value. 

This is why building on Kubernetes was a natural choice for us. Kubernetes gives Microsoft 365 the ability to run and grow at the scale the service demands without sacrificing consistency. But we also knew that growth can increase system complexity without the right management in place. As services and team sizes increase, we needed systems that mitigate these issues.  

Infrastructure and operational complexity grows faster than teams unless the platform absorbs that complexity. Service teams historically solved infrastructure challenges independently. Each team was able to create their own solution with Azure, but without a standardized platform, we risked trending towards unnecessary operational overhead. As services scaled, we needed to mitigate the reality of: 

Inconsistency and configuration drift across environments

Increased infrastructure work pulling developers away from product work

Increased risk and uncertainty in deployments and change management

We needed a platform layer that could absorb this complexity before it became a tax on every team.

Solution: Evolving the operations experience 

Microsoft 365 uses AKS as the foundation for a standardized hosting layer. AKS provides the orchestration, Azure integration, and operational primitives needed for large-scale environments. Teams builds on that foundation with Microsoft 365-specific patterns, guardrails, and workflows.

That hosting layer gives teams a more consistent path from onboarding to production. Provisioning is aligned to predefined architectures and regional boundaries. Security and compliance controls are applied centrally instead of left to every service team to implement independently. Standardized deployment practices reduce change risk, while shared telemetry improves visibility into health and policy adherence.

The result is a model where developers hand over service intent and application code, while the platform supplies the hosted environment, deployment safety, security and compliance guardrails, and operational scaffolding needed to run well at scale.

COSMIC: Microsoft 365’s Platform Hosting Layer 

This is exactly why we created COSMIC which is Microsoft 365’s platform engineering layer for standardizing hyper-scale cloud services on AKS. Our goal with COSMIC and its platform engineering team was simple: “give us the code and allow us to do the rest.”

COSMIC was designed to create a secure, compliant, common tech stack that removes infrastructure burden from application teams, allowing them to focus on innovative feature work while COSMIC provides a full-service, standardized platform. It functions as an interface layer on top of AKS and, with the help of the COSMIC team, tailors the experience to Microsoft 365’s needs: 

A secure and compliant default posture. Services inherit standardized controls for identity, access, certificates and secrets, approved base images, and policy enforcement.
A streamlined provisioning and onboarding path. Teams are mapped to predefined deployment shapes, regional placement patterns, and hosted environments that reduce setup friction and improve consistency.
Safer deployments and stronger resiliency. Standard rollout patterns, stage validation, telemetry-driven checks, and controlled change boundaries help teams release with lower risk and recover more predictably.
Operational efficiency at scale. Shared observability, common dashboards, and platform-managed runtime practices reduce duplicated effort while helping teams focus on feature delivery instead of infrastructure mechanics.

At a high level, product teams submit a request to COSMIC for the infrastructure and services needed to run their workloads. Based on a service’s requirements, COSMIC provisions infrastructure using standardized architectures with built-in security, compliance, and regional controls. The platform also helps place workloads efficiently and manage capacity at scale.

Once infrastructure is provisioned, teams adopt standardized deployment and operational workflows that automatically inherit Microsoft 365 security, compliance, and reliability standards.

This includes:

Identity, authorization, and secrets management: standardized authentication and authorization patterns, automated certificate management, and centralized secrets management using Azure Key Vault to provide consistent credential handling across the service lifecycle
Standardized and secure runtime environments: standardized base container images with enforced patching and security updates to keep workloads current with the latest security and platform improvements
Built-in resiliency and scalable operations: automated scaling, regional placement controls, health-based recovery, and deployment safety mechanisms to help services remain reliable during traffic spikes, failures, and growth
Rich observability and telemetry: standardized logging, metrics, and monitoring that help teams detect, diagnose, and mitigate issues across both the COSMIC platform and the applications running on it.
Managed deployments and infrastructure automation: centralized deployment systems with built-in validation, compliance enforcement, safe rollout practices, and automated recovery. Infrastructure and environment configuration are standardized through reusable templates and automated workflows, reducing operational overhead as services scale.

Impact: A standardized platform that delights developers

For Microsoft 365 service teams, COSMIC makes the hosted experience more predictable. Teams do not have to become experts in every layer of platform operations in order to build and run business-critical services. Instead, we unlock:

Faster, more consistent deployments – shipping to production is simpler and more predictable, reducing decision fatigue for developers.

Team autonomy preserved - service teams keep their choice in availability using a self-managed environment within COSMIC’s guardrails.

Security and compliance by default – trust requirements are “baked in” to the experience and enforced through the platform, not through manual checklists.

COSMIC is now one of the most widely-adopted internal platforms at Microsoft, with a continually positive growth trend. It’s one of our clearest win-win outcomes: developers focus on the work they love while the platform team maintains systems as the experts in operational excellence.

Learnings: Building your own platform 

Operating Kubernetes at enterprise scale requires simplifying trust, compliance, and reliability into the platform. Additionally, developer experience is key: developer and product team autonomy scales best when guardrails are strong and experience is consistent. 

These properties don’t emerge organically; they require a modern operating model driven by a team of platform experts.

When creating your organization’s model, we recommend keeping some of our learnings in mind:

Limit blast radius in change management - safe deployment practices for all changes are critical. Changes are contained within defined boundaries, with the ability to reroute traffic or fail over to backup services to minimize risk. Every deployment follows the same standardized validation and rollout process.

Create a turnkey experience for service teams - product teams should focus on building great user experiences, not becoming infrastructure experts. COSMIC abstracts away operational complexity such as cluster configuration, patching, scaling policies, pod disruption management, and image lifecycle management so teams can move faster with less operational overhead.

Resiliency and best practices baked in - services inherit platform-level resiliency patterns by default, including automated scaling, health-based recovery, deployment safety checks, regional distribution, and standardized operational guardrails. This helps teams build reliable services without having to reimplement foundational operational practices themselves.

Aggregate observability around what matters - teams get pre-built dashboards and standardized telemetry experiences, while role-based access controls ensure the right people see the right data. Service teams can focus on their application health, while platform operators monitor fleet-wide trends across reliability, performance, utilization, and cost efficiency. This helps reduce noise and surface the signals that matter most.

Turning learnings into features 

Microsoft has absorbed the hardest parts of operating Kubernetes at scale and encoded lessons from COSMIC into Azure Kubernetes Service. Through those learnings, we build features that minimize pain points for our customers. Our experience with COSMIC informed new features that make building your own platform faster and easier:

AKS Automatic: this is how we bring the simplified experience developers needed to customers. AKS Automatic lets developers to create production-ready Kubernetes clusters with built-in best practices and guardrails while Azure handles the node management, scaling, and security.

Azure Kubernetes Fleet Manager: Operating a large, globally distributed fleet requires predictable, low risk ways to coordinate safe multi-cluster upgrades, load balance traffic across clusters, and centralize control across regions and clouds. The same capabilities that enable fleet-level orchestration for ourselves are available for our customers.

Expanded observability: Managed Prometheus and Grafana are integrated with AKS and Azure Monitor for secure, compliant, and cost-effective monitoring, enabling actionable insights at scale without drowning in data or compromising on security and compliance.