One of the most common mistakes I see Pega LSAs and Architects make has nothing to do with technical skills.
It is failing to document the architectural decisions they make during implementation.
Every greenfield application or major release usually starts the same way. Days, or even weeks, are spent discussing architectural choices. Divide and conquer strategies. Microservice based architectures. Straight Through Processing (STP) flows. Data first design approaches. Framework design. Integration patterns.
Architects invest a significant amount of time deciding how an application should be built.
Then the decisions are made, development begins, and the most important part is forgotten.
Nobody documents why those decisions were made.
The 2018 Application Nobody Can Explain Today
Imagine an application that was built in 2018.
It has a strong framework layer with separate presentation, application service, business service, integration, and data layers. At the time, that was considered a solid architectural approach and aligned with industry best practices.
Fast forward to today.
A new architect joins the project and asks,
“Why was it designed this way? Why not microservices?”
The answer is simple.
Because those decisions were right for that point in time.
There is no universally right or wrong architecture. Every decision depends on business requirements, compliance, timelines, team maturity, technology limitations, future roadmap, and many other factors.
What looked like the best solution in 2018 may not be the approach you would choose in 2026.
That is not bad architecture.
That is simply how architecture evolves.
The real problem begins when nobody remembers why those decisions were taken.
Architects Move On. Applications Don’t.
Architects rarely stay on the same project forever.
People change roles. Move to different clients. Join new companies. That is completely normal.
Applications, however, often live for ten years or more.
If the reasoning behind important architectural decisions exists only inside someone’s head, that knowledge disappears the moment they leave.
That is why documenting architecture decisions should never be considered optional.
If you decide to implement divide and conquer instead of a single case design, choose asynchronous messaging over synchronous integration, or introduce a framework layer, document the reasoning behind it.
Someone will eventually inherit the application.
Give them more than diagrams.
Give them context.
Where Blueprint Fits Into the Picture
Pega Blueprint now stores supporting requirements and generated assets as part of the case itself, and it genuinely works well as a repository for early business requirements and solution discussions. This is a real step forward for how architecture conversations get captured from day one.
As of 2026, most organizations will still want to pair Blueprint with their existing documentation setup, since archival strategies, governance, and long-term retention practices around it are still evolving.
Most organizations continue to rely on Confluence, SharePoint, Wiki pages, or other knowledge repositories to preserve project artifacts over the lifetime of an application.
And those repositories should contain much more than architecture diagrams.
Design documents.
Architecture Decision Records (ADRs).
Upgrade preparation runbooks.
Deployment guides.
API specifications.
Integration contracts.
Security considerations.
Most importantly, they should capture the reasoning behind the decisions, not just the implementation itself.
Document the “Why”, Not Just the “What”
Documentation should never stop at describing what was built.
It should explain why it was built that way.
Five years later, that “why” becomes significantly more valuable than the implementation itself.
Many architects dislike documentation because it feels like extra work after the real engineering is finished.
In reality, documentation is part of the engineering.
It is one of the few things that continues to provide value long after the implementation is complete.
A Responsibility Every LSA Should Embrace
As you grow into an LSA or Architect role, documenting your implementations, architectural trade-offs, assumptions, and key decisions should become second nature.
It is no longer just good practice.
It is part of the responsibility that comes with the role.
Great architects do not just build applications.
They leave behind the knowledge that allows those applications to evolve long after they have moved on.
