# Sharing scalability: skew, recalculation and role optimization

*Platform Sharing and Visibility Architect Study Guide · Implications of Security Model Choice · Last updated October 26, 2026 · https://www.certifyforce.com/study-guide/platform-sharing-and-visibility-architect/implications-of-security-model-choice/sharing-scalability-skew-recalculation-and-role-optimization*

Why ownership skew, parent-child skew and group membership locking slow a sharing model, what a role or owner change really recalculates, when to defer sharing calculations, and how account role optimization and power users keep external roles under the allocation.

- Certification: Salesforce Platform Sharing and Visibility Architect
- Exam section: Implications of Security Model Choice
- Study guide: https://www.certifyforce.com/study-guide/platform-sharing-and-visibility-architect

**Official exam objective:**

> Given a scenario, determine the scalability implications of the sharing solution.

## What the exam expects

- Spot ownership and parent-child skew and pick the documented fix.
- Remove sharing the platform doesn't need: redundant rules, needless hierarchy access, mass manual shares.
- Predict what a user move, role move or external account owner change recalculates, and plan realignments.
- Decide when deferred sharing calculation helps, and respond to group membership locking errors.
- Size external roles with account role optimization and person account owner power users.

Key terms: **ownership skew** (one user or queue owning more than 10,000 records of an object); **parent-child skew** (more than 10,000 children on one parent account); **deferred sharing calculation** (suspended recalculation, enabled by Support); **group membership locking** (table locks during role and group updates); **account role optimization** (ARO: one shared person role for a lone role-based external user).

## Key facts

| Fact | Detail | Source |
|---|---|---|
| Ownership skew | Over 10,000 records of an object per user or queue | [Sharing performance](https://help.salesforce.com/s/articleView?id=platform.security_sharing_performance.htm&language=en_US&type=5) |
| Parent-child skew | Over 10,000 children on one account | [Sharing performance](https://help.salesforce.com/s/articleView?id=platform.security_sharing_performance.htm&language=en_US&type=5) |
| Structural realignments | No more than quarterly (rule of thumb) | [Platform Sharing Architecture](https://architect.salesforce.com/docs/architect/fundamentals/guide/platform-sharing-architecture) |
| Deferral | Support enables; resume plus full recalculation | [Defer Sharing Calculations](https://help.salesforce.com/s/articleView?id=platform.security_sharing_defer_sharing_calculations.htm&language=en_US&type=5) |
| Locking during deployments | Wait for the deployment or tests | [Group Membership Locking](https://developer.salesforce.com/docs/atlas.en-us.draes.meta/draes/draes_group_membership_locking.htm) |
| External role allocation | 50,000 roles | [Optimize Account Roles](https://help.salesforce.com/s/articleView?id=platform.networks_partners_optimize_roles.htm&language=en_US&type=5) |
| Detail object | No share object | [Sharing a Record Using Apex](https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_bulk_sharing_creating_with_apex.htm) |

## Check yourself

- Why does losing access to one contact on a skewed account slow the update?
- When should a public group's Grant Access Using Hierarchies be deselected?
- Which change triggers only group membership calculation?
- Why can't power users be created mid-migration under deferral?

## Sources

- [Best Practices for Optimizing Sharing Performance](https://help.salesforce.com/s/articleView?id=platform.security_sharing_performance.htm&language=en_US&type=5)
- [Platform Sharing Architecture](https://architect.salesforce.com/docs/architect/fundamentals/guide/platform-sharing-architecture)
- [Defer Sharing Calculations](https://help.salesforce.com/s/articleView?id=platform.security_sharing_defer_sharing_calculations.htm&language=en_US&type=5)
- [Group Membership Operations and Sharing Recalculation](https://developer.salesforce.com/docs/atlas.en-us.draes.meta/draes/draes_group_membership.htm)
- [Group Membership Locking](https://developer.salesforce.com/docs/atlas.en-us.draes.meta/draes/draes_group_membership_locking.htm)
- [Parent-Child Data Skew](https://developer.salesforce.com/docs/atlas.en-us.draes.meta/draes/draes_object_relationships_parent_child_data_skew.htm)
- [Optimize Account Roles to Improve Performance and Scale](https://help.salesforce.com/s/articleView?id=platform.networks_partners_optimize_roles.htm&language=en_US&type=5)
- [Architect Salesforce Record Ownership Skew for Peak Performance in LDV Environments](https://developer.salesforce.com/blogs/engineering/2012/06/architect-salesforce-record-ownership-skew-for-peak-performance-in-large-data-volume-environments)
- [Defer Sharing Calculation (Large Data Volumes best practices)](https://developer.salesforce.com/docs/platform/salesforce-large-data-volumes-bp/guide/ldv-deployments-techniques-deferred-sharing-calculation.html)
- [Sharing a Record Using Apex](https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_bulk_sharing_creating_with_apex.htm)
- [Restriction Rule Considerations](https://help.salesforce.com/s/articleView?id=platform.security_restriction_rule_considerations.htm&language=en_US&type=5)

## About the full unit

The "Core concepts", "Exam traps" and "Worked scenario" sections of this unit, its 18 linked practice questions, and unlimited timed mock exams are included with the Platform Sharing and Visibility Architect pack (USD $19): https://www.certifyforce.com/practice-exams