Great thread — this is exactly the kind of real-world perspective that helps teams make informed decisions.

From my experience working on O11 to ODC migrations, here are the things that tend to surprise teams the most:

Planning — phased wins every time. Big-bang migrations are very high risk in ODC because the architectural shift is significant, not just a lift-and-shift. The approach that works best is to identify a bounded domain (ideally a self-contained app or set of apps with limited cross-app dependencies) and migrate that first. This gives you a real proof-of-concept with production stakes and surfaces the unknowns early.

Biggest technical shift: the integration model. Integration Studio extensions don't exist in ODC — everything becomes External Libraries (C# NuGet packages). If your O11 apps rely heavily on custom extensions, budget significant time here. The good news is the pattern is clean once you learn it, and it forces better separation of concerns.

Identity model is a full redesign. O11's Users entity and built-in auth don't map directly to ODC. ODC has a native IdP, supports OIDC/SAML external providers, and the end-user identity concepts are different. If you have custom auth, role logic, or multi-tenant user management, plan this carefully upfront — it touches everything.

Timeline reality check. Teams consistently underestimate by 30–50% on their first ODC migration. The tooling (Migration Assessment Tool) is helpful for flagging incompatible patterns, but the actual refactoring — especially around service actions, consumed REST/SOAP APIs, and the new library model — takes time to get right.

Post-migration upsides that are real. The CI/CD pipeline in ODC is genuinely better. Deployment zones, the container-based runtime, and the governance model around libraries and services are a step forward architecturally. Teams that push through the migration pain typically don't want to go back.

Happy to go deeper on any specific area — the identity model and External Libraries tend to be the biggest sticking points in practice.

Great thread — this is exactly the kind of real-world perspective that helps teams make informed decisions.

From my experience working on O11 to ODC migrations, here are the things that tend to surprise teams the most:

Planning — phased wins every time. Big-bang migrations are very high risk in ODC because the architectural shift is significant, not just a lift-and-shift. The approach that works best is to identify a bounded domain (ideally a self-contained app or set of apps with limited cross-app dependencies) and migrate that first. This gives you a real proof-of-concept with production stakes and surfaces the unknowns early.

Biggest technical shift: the integration model. Integration Studio extensions don't exist in ODC — everything becomes External Libraries (C# NuGet packages). If your O11 apps rely heavily on custom extensions, budget significant time here. The good news is the pattern is clean once you learn it, and it forces better separation of concerns.

Identity model is a full redesign. O11's Users entity and built-in auth don't map directly to ODC. ODC has a native IdP, supports OIDC/SAML external providers, and the end-user identity concepts are different. If you have custom auth, role logic, or multi-tenant user management, plan this carefully upfront — it touches everything.

Timeline reality check. Teams consistently underestimate by 30–50% on their first ODC migration. The tooling (Migration Assessment Tool) is helpful for flagging incompatible patterns, but the actual refactoring — especially around service actions, consumed REST/SOAP APIs, and the new library model — takes time to get right.

Post-migration upsides that are real. The CI/CD pipeline in ODC is genuinely better. Deployment zones, the container-based runtime, and the governance model around libraries and services are a step forward architecturally. Teams that push through the migration pain typically don't want to go back.

Happy to go deeper on any specific area — the identity model and External Libraries tend to be the biggest sticking points in practice.