Part 3b — Data Aggregation

Source of truth for design decisions: https://github.com/alan-eu/Topics/discussions/32979 ⧉

Where the code lives

All 3b query code lives under backend/components/payroll_tool/internal/business_logic/queries/data/.

Public entry points are exposed via backend/components/payroll_tool/public/api.py (added by Task 14 of the 3b implementation stack).

Implementation stack

The 3b implementation is split into 17 stacked PRs — see Linear PAY-1839 for the parent and the full sub-task list (PAY-1840 → PAY-1856).

High-level layering (framing §3):

• Layer A — raw data: filter, join, group, aggregate, sort, paginate.
• Layer B — formatting: per-column rendering using FormatConfig.

Adjacent framings (context)

• Part 1 / 1.5 — scope and overall architecture.
• Part 2 — PayrollChange generation (model and pipeline).
• Part 3a — PayrollTemplate / PayrollColumnDefinition / interface contract.
• Part 3c — UI + export surface (consumes 3b's get_payroll_data).