SaaS Scaling: Streamlining Governance Across Multiple AWS Accounts with Automated SCP Management

Hi Hashnode Community,

Sharing knowledge is one of the best ways to grow together, and this week I’m excited to explore a critical topic for SaaS businesses: streamlining AWS account management to scale effectively while reducing complexity.

One innovator that comes to mind with thousands of AWS accounts, powering their microservices and millions of daily transactions is Netflix.

Netflix’s refined approach to cloud management offers many lessons. For one, focusing on security at scale. With its multi-account setup, Netflix follows stringent security practices.

Unlike many organisations that rely on complex Organisational Unit (OU) hierarchies, Netflix keeps its AWS Organisations structure relatively flat, preferring simplicity and automation to manage scalability.

Let’s explore the key pillars.

Key Pillars of Netflix’s AWS Account Management

1. Account Isolation for Scalability and Security

Netflix isolates workloads, environments, and teams into separate AWS accounts. This approach ensures:

• Minimal Blast Radius: A security breach or misconfiguration in one account does not affect others.

• Operational Independence: Teams can manage their own accounts without worrying about interfering with other services.

• Cost Allocation: Clear separation of resources allows precise cost tracking for individual teams or projects.

Netflix’s culture emphasises developer autonomy.

To enable this:

Firstly, developers are given access to manage their accounts and resources independently. SCPs and automation ensure that even with autonomy, security and compliance are maintained.

Ensuring consistent policy enforcement with Service Control Policies (SCPs) require a design that enables a SaaS to scale without any issues. SCPs are powerful guardrails to help protect resources and ensure compliance.

If done right, the security, governance and scalability pitfalls can be avoided.

When it comes to SCPs, simplicity is the goal.

Here’s why SCPs Matter:

• Ensure tenant isolation and prevent unauthorised access to shared resources.

• Enforce compliance with data residency and regulatory standards (e.g., GDPR, CCPA).

• Benefits:

• Simplified multi-tenant architecture management.

• Enhanced customer trust with enforced security practices.

Let’s explore what happens when multiple accounts share the same OU.

1. Policy Complexity: Large, complex SCPs can become hard to manage and debug.

2. Unintended Restrictions: Broad SCPs may inadvertently block legitimate actions across multiple accounts.

3. Management Overhead: Adding or removing accounts can require extensive re-evaluation of policies.

4. Policy Evaluation Overload: SCPs applied at multiple levels (root, OU, account) increase evaluation time and complexity.

By embedding automation into your SCP management and account setup processes, you can eliminate scalability issues, improve governance, and focus on strategic growth.

SaaS Scaling Rapidly

• Why SCPs Matter:

• Prevent over-provisioning or costly mistakes as new accounts are added quickly.

• Establish guardrails for DevOps teams without slowing down innovation.

• Benefits:

• Cost control through policies limiting the use of expensive resources.

• Secure scaling with consistent governance across accounts.

For example, SaaS expanding to new markets or regions and adding new teams.

Key Challenges without automation and modularity can result in the following:

Redundant or Conflicting Service Control Policies

Policy Sprawl: Managing numerous SCPs across multiple accounts within the same OU can lead to redundant or conflicting policies.

A Single OU with many accounts.

Slow policy propagation and administration overhead

Operational Bottlenecks: A single OU with too many accounts can slow down policy propagation and increase administrative overhead.

No Logical Grouping

Limited Segmentation: Lack of logical grouping within the OU can make troubleshooting and governance more difficult.

No Scope

Performance Impact: Improperly scoped SCPs may inadvertently restrict necessary actions, impacting system performance.

Manage Governance and Security with Automation

Imagine having to administer and manage thousands of accounts in a single OU without automation. It becomes impossible as the startup grows.

Let’s take some action to avoid the pitfalls mentioned above.

Actionable Steps:

1. Automate OU and Account Segmentation

• Solution: Use automation tools like AWS Organisations API and AWS Control Tower to create and organise accounts.

Automation:

• Automate account creation with predefined SCPs using AWS Service Catalog and custom provisioning templates.

• Leverage Control Tower lifecycle events to trigger account configuration workflows.

2. Automate SCP Creation and Deployment

• Solution: Use Infrastructure as Code (IaC) tools like AWS CloudFormation, Terraform, or CDK to define and manage SCPs.

Action:

• Create reusable SCP templates in YAML or JSON.

• Deploy SCPs automatically using pipelines (e.g., AWS CodePipeline) triggered by changes in version control systems like Git.

3. Dynamic SCP Assignment Using Tags

• Solution: Automate SCP assignment based on account tags using AWS Lambda functions or step functions.

Action:

1. Tag accounts (e.g., Environment=Prod, Team=DevOps).

2. Use a Lambda function triggered by AWS Config to evaluate account tags and apply corresponding SCPs dynamically.

3. Example workflow:

• Tag detection: A new account is tagged as Environment=Dev.

• SCP application: Lambda applies a “Restricted Regions” SCP to limit actions outside approved regions.

4. Monitoring and Compliance Enforcement

• Solution: Automate compliance monitoring and enforcement using AWS Config Rules and CloudWatch Alarms.

Action:

• Create custom Config Rules to validate SCP compliance across accounts.

• Trigger automated remediation actions using AWS Systems Manager Automation Documents (SSM Documents) or Lambda when violations occur.

• Set up alerts in CloudWatch to notify administrators of policy deviations.

5. Continuous Audit and Reporting

• Solution: Use automation to maintain an audit trail of SCP changes and their impact.

Action:

• Enable AWS CloudTrail to log SCP creation, modification, and application events.

• Use AWS Athena and Amazon QuickSight to generate visual reports on SCP effectiveness and compliance.

Let’s look at an example.

Here’s an Example Automation Workflow

Let’s consider a scenario. A SaaS company manages hundred AWS accounts across Dev, Prod, and Finance environments. SCP’s need to be enforced automatically.

1. Account Setup:

• Use AWS Control Tower to provision accounts with predefined tags (e.g., Environment, Department).

• Trigger workflows to configure baseline SCPs for each account type.

2. Dynamic Policy Assignment:

• An account tagged Environment=Prod automatically receives:

• An SCP restricting access to unapproved regions.

• An SCP enforcing multi-factor authentication (MFA) for administrative actions.

• Automation pipeline:

• Trigger: AWS Config detects account tags.

• Action: Lambda applies the appropriate SCP using AWS Organisations API.

3. Policy Compliance Monitoring:

• AWS Config evaluates all accounts for compliance with mandatory SCPs.

• Non-compliant accounts trigger automated remediation actions:

• Example: Enable logging and auditing features if missing.

4. Reporting:

• Use CloudTrail logs to track SCP deployment events.

• Generate compliance dashboards in QuickSight, showing policy adherence and areas requiring attention.

Pro Tip: Automate Testing Before SCP Deployment

• Use AWS Policy Simulator to test SCPs in a sandboxed environment.

• Automate these tests using CI/CD pipelines to validate changes before production deployment.

Following best practices from the outset will reduce complexity and scalability issues in the long-term.

Best Practices for Avoiding Scalability Issues

1. Keep SCPs Modular and Reusable

The way to go is modularity. Smaller reusable components for the sake of ease when troubleshooting and management overload.

Instead of writing monolithic SCPs, break them into smaller, reusable policies. Modular SCPs are easier to manage and debug.

• Example: Instead of a single SCP for all guardrails, create separate policies for:

• Region restrictions.

• Service restrictions.

• Compliance requirements.

Modular SCPs can be attached selectively to different OUs or accounts, reducing duplication and management complexity.

2. Use Policy Conditions for Granularity

Conditions in SCPs allow you to apply rules dynamically, reducing the need for multiple policies.

Using conditions like aws:RequestTag or aws:PrincipalOrgID to further refine access controls.

3. Limit SCP Attachments

AWS evaluates SCPs attached at the root, OU, and account levels. Attaching too many SCPs can slow down policy evaluation and complicate debugging.

• Recommendation: Attach SCPs primarily at the OU level to enforce shared rules, and avoid direct attachments to individual accounts unless absolutely necessary.

4. Automate SCP Management

Manually managing SCPs for a large number of accounts is not scalable. Use Infrastructure as Code (IaC) and automation tools to streamline management:

• AWS CloudFormation: Define and deploy SCPs programmatically.

• AWS CDK or Terraform: Automate SCP creation and updates.

• Use version control (e.g., Git) to track SCP changes and maintain a history of updates.

5. Group Accounts Logically

If a single OU contains accounts with vastly different use cases, it can lead to overly broad SCPs. Instead:

• Group accounts within the OU based on shared requirements.

• If necessary, split accounts into multiple OUs for more precise SCP application.

6. Use AWS Control Tower for Governance

AWS Control Tower simplifies multi-account management by automating the application of SCPs (called Guardrails) to OUs.

• Pre-built guardrails address common use cases, such as:

• Preventing public S3 buckets.

• Enforcing CloudTrail logging.

• Automatically applies SCPs when new accounts are created.

7. Monitor and Audit SCP Effectiveness

Regular monitoring ensures SCPs are working as intended and do not block legitimate operations:

• CloudTrail: Track denied actions caused by SCPs.

• AWS Config: Use Config Rules to ensure accounts comply with SCP requirements.

• IAM Policy Simulator: Test SCPs before deployment to avoid unintended restrictions.

8. Delegate Administrative Control

As the number of accounts grows, centralising SCP management can become a bottleneck. Use delegated administrators to distribute management responsibilities across teams or departments.

• Example: Allow a specific team to manage SCPs for sandbox accounts while retaining control over production.

9. Optimise Organisational Structure

To avoid scalability issues:

• Use a flat OU structure where possible (limit depth to 2–3 levels).

• Minimise the number of accounts in a single OU if they have divergent requirements.

10. Understand AWS Limits

Be aware of the limits for AWS Organisations and SCPs:

• Max SCP size: 5,120 characters.

• Max SCPs per account: 5.

• Max SCPs in an organization: 300.

If you approach these limits, consolidate policies and work with AWS Support for potential extensions.

Organisations looking to scale their AWS usage can learn valuable lessons from Netflix’s approach.

Implement the following to ensure SaaS growth, scalability and governance that sets you up for the long-term.

1. Adopt a Multi-Account Strategy: Isolate teams, workloads, and environments to reduce complexity and risks.

2. Use Guardrails, Not Roadblocks: Empower teams while enforcing non-negotiable rules with SCPs and automation.

3. Automate Everything: From account creation to policy enforcement, automation ensures consistency and efficiency.

4. Invest in Internal Tools: Custom tools tailored to your SaaS needs can streamline cloud management.

5. Monitor Continuously: Centralised logging and monitoring are essential for security and compliance in a multi-account setup.

Final Thoughts

Every SaaS needs a strategic approach to scalability and governance. Adopting the SIMPLe framework: SIMPLe as well as following best practices ensures growth.

Scaling Service Control Policies (SCPs) for multiple accounts in one OU requires thoughtful planning and the right tools.

By adopting modular SCPs, leveraging automation, and monitoring policies proactively, you can avoid common scalability issues. These best practices ensure your SaaS remains secure, compliant, and operationally efficient as it grows.

Ready to take control of your multi-account environment?

Take your learning to the next level for a strategic perspective: Explore further:Sync Nimbus Strategic Insights

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