T1 — Interface
Interface is the bit your staff or customers actually touch — built in Next.js or Astro depending on whether the tool is interactive or document-shaped. No design system bought off the shelf, no Bootstrap, no Material. The UI matches your existing brand and is sized for the actual screens it’ll be used on (often a second monitor at 1280, not a designer’s 27”).
T2 — Data
Data is a single Postgres database, migration files in version control, and a clean schema you can read in an afternoon. Every record carries audit metadata — who, when, from where — and every destructive operation soft-deletes. Backups run nightly to an off-host store. If the app ever has to die, your data leaves as a clean SQL dump.
T3 — AI workload
AI workload is the deliberate bit: which step in the workflow benefits from a model, which model, with what context, on what budget. I write the prompts as code rather than configuration; the evaluation harness lives in the repo; the model is a configuration value that can be swapped without a redeploy. Where retrieval makes sense, vector storage rides on pgvector inside the same Postgres.
T4 — Operations
Operations is everything that keeps the thing alive after I’m gone. Auth (your Google Workspace, or magic links, or a real password — whichever fits), staging and production environments, log aggregation, an admin view of the AI’s actual costs, and a runbook short enough that the next developer can read it on a train.