3.1 · Platform Architect · Operating Model
Book 1 · Ch 12 · Product Boundaries That Hold

L2-to-L3 Transition Plan: Mixed-Fleet Operating Model

How to run a managed service and a self-serve platform simultaneously without breaking either. Resource allocation, customer migration sequence, and sunset criteria. Specific timelines populate once L3 GA date is confirmed.

3.1 · Platform Architect · artifact id: l2-to-l3-transition-plan-v0.html · v0 · 2026-05-28
Format stub. The mixed-fleet operating model, resource allocation principles, migration sequence, and sunset criteria are established. Specific customer names, migration dates, and engineering headcount allocations populate once the L3 GA date is confirmed and the customer count on L2 is known.

Why boundaries matter most during transition

Ch 12 of Shrink-Wrap It identifies the transition period as the highest-risk phase for boundary violations: "Before agreeing to any feature involving new data flows, new integrations, or new data types, consult your ISSO or compliance team. What seems like a simple enhancement may constitute a boundary change." During the L2-to-L3 transition, NorthAI is running two product modes simultaneously. A boundary change in one mode can cascade to the other if the architecture is not cleanly separated.

This plan treats L2 and L3 as distinct authorization boundary states during the transition period. L2 customers remain on the original SSP. L3 customers are on the updated SSP that includes the self-serve control plane. These are two different system boundaries until the last L2 customer migrates.

Mixed-fleet operating model

Two-track operation

Dimension L2 track (existing customers) L3 track (new customers + migrated L2)
Provisioning Manual runbook; NorthAI ops staff; 1-2 week SLA Self-serve portal; API-driven; 24-hour SLA
Authorization boundary Original SSP; 3PAO assessed; existing ATO covers L2 customers Updated SSP includes control plane API; 3PAO assessed; separate ATO or ATO modification required
ConMon Original ConMon scope; existing scanning and POA&M procedures Expanded ConMon scope covers control plane; additional scanning targets; larger POA&M surface
Customer success NorthAI CS actively manages all L2 customers; manual touchpoints per nps-outcome-cadence-v0 Reduced CS involvement for L3; product-led support; escalation path still maintained
Incident response L2 incident affects only L2 customers; L3 unaffected (separate infrastructure) L3 incident affects only L3 customers; L2 unaffected
Engineering support Maintenance mode after L3 launch; bug fixes only; no new features Active development; new features, optional modules, marketplace integrations

Resource allocation during transition

The mixed-fleet period creates a resource split that must be planned explicitly. The default allocation below shifts over the transition period. Engineering head count numbers are placeholders.

Period L2 allocation L3 allocation Rationale
Pre-L3 launch (through Q8) 80% engineering; 100% ops; 100% CS 20% engineering (control plane build); 0% ops; 0% CS L2 is the revenue engine; L3 build is background investment. Do not starve L2 ops.
L3 launch through 50% migration 50% engineering; 60% ops; 60% CS 50% engineering; 40% ops; 40% CS Parallel operation; new customers on L3; L2 customers still need full support during migration planning
50% migration through final migration 20% engineering; 30% ops; 30% CS 80% engineering; 70% ops; 70% CS L2 is winding down; investment shifts to L3; L2 ops maintained until last customer migrates
Post-migration (L3 only) 0% (L2 sunset) 100% engineering; 100% ops; 100% CS Full investment in L3; no mixed-fleet overhead; ConMon scope simplified

Customer migration sequence

The migration sequence is not first-in, first-out. It is risk-ordered: migrate customers whose migration poses the least authorization risk and disruption first, then work toward the most complex migrations.

Migration priority Customer profile Why this priority
Priority 1 Customers with the fewest Zone 3 (optional module) customizations; lowest integration complexity; smallest user counts Lowest migration risk; fastest to validate L3 migration process; builds confidence before complex customers
Priority 2 New customers onboarded after L3 launch; they never had L2 infrastructure; no migration needed, just L3 from start Zero migration cost; these customers validate L3 natively; track separately from migration metrics
Priority 3 Customers with medium complexity: 1-2 Zone 3 modules, moderate user counts, standard ICAM integration Migration process is validated from Priority 1; apply lessons learned; allow 2-3 week migration window per customer
Priority 4 Customers with highest complexity: custom ICAM integrations, multiple Zone 3 modules, large user counts, or specific ATO constraints Migrate last; most stakeholder management required; may require a dedicated migration sprint per customer

Migration playbook per customer

Step Activity Timeline Owner
1 Migration briefing: explain L3 benefits, migration process, and the absence of service disruption to agency PM and ISSO Week 1 Customer Success
2 L3 tenant provisioning: stand up new L3 tenant in parallel; do not decommission L2 environment yet Week 1-2 Platform Architect
3 Data migration: copy existing configuration, audit logs, and user roster from L2 to L3 tenant; validate completeness Week 2-3 Platform Architect
4 Parallel running: L3 tenant is live but L2 is still primary; agency runs both for 5-7 business days; no disruption to production Week 3-4 Platform Architect + Customer Success
5 Cutover: agency ISSO confirms L3 readiness; cutover switch thrown; L2 decommissioning scheduled End of Week 4 Authorization Architect + Agency ISSO
6 L2 decommission: after 30-day post-cutover monitoring period with no issues; L2 environment removed from inventory Week 8 (30 days post-cutover) Platform Architect

L2 sunset criteria

L2 is fully sunset when all of the following are true:

Boundary discipline during sunset

The L2 decommission process is itself a boundary change event. Every L2 environment removed from the authorization boundary must be documented in the SSP as a scope reduction. The 3PAO must confirm the reduction does not inadvertently remove a control that was shared between L2 and L3. Treat sunset as a mini-assessment, not a cleanup task.