Django App Development

Overview

Use this skill to implement Django changes with explicit domain boundaries, safe migrations, and operationally predictable behavior.

Scope Boundaries

• Use this skill when the task matches the trigger condition described in description.
• Do not use this skill when the primary task falls outside this skill's domain.

Shared References

• Layering and boundary guidance:
  • references/django-layering-guidelines.md

Templates And Assets

• Change planning template:
  • assets/django-change-plan-template.md
• Migration safety checklist:
  • assets/django-migration-safety-checklist.md

Inputs To Gather

• Feature requirements and affected domain boundaries.
• Existing app/module structure and cross-app dependencies.
• Data model constraints, traffic profile, and migration risk tolerance.
• Authentication/authorization expectations and operational requirements.
• Serializer/form input shapes and domain command object contracts.

Deliverables

• App change design (models, views, forms/serializers, services/managers).
• Migration plan with rollout/rollback notes and data-safety checks.
• Security and permission model updates for affected routes/actions.
• Verification checklist (tests, manual checks, observability points).

Quick Example

• Keep view/controller thin; move domain rules into service layer or model manager.
• Add DB constraints/indexes for integrity and query patterns, not only ORM-level validation.
• Use explicit transaction boundaries for multi-write critical flows.
• Fail fast when required environment variables are missing from settings.
• Convert serializer/form payloads to explicit typed command objects before domain service calls.

Quality Standard

• App boundaries are cohesive and avoid circular dependency patterns.
• Migrations are reviewed for lock risk, backfill strategy, and reversibility policy.
• Authn/authz is explicit on every protected path.
• Error handling and logging expose failures without silent fallback behavior.
• Domain services receive explicit typed contracts, minimizing repeated casts and shape checks.

Workflow

1. Scope impacted apps and define boundary-safe change plan in assets/django-change-plan-template.md.
2. Implement model and domain logic with explicit constraints.
3. Update views/forms/serializers while keeping transport and domain concerns separated.
4. Map request payloads to explicit typed structures (dataclass/TypedDict/Pydantic) rather than passing loose dicts through domain boundaries.
5. Create and review migrations with operational safety checks from assets/django-migration-safety-checklist.md.
6. Validate with tests and critical-flow verification before release.

Failure Conditions

• Stop when domain responsibilities are spread across unrelated apps.
• Stop when migrations can cause unacceptable lock/data-loss risk without mitigation.
• Escalate when permission model changes are unclear or unverified.