Core Software Patterns Everyone Should Know

This isn’t just about what I’ve been building lately—it’s about the software habits and architectural patterns that prepare us for long-term success. Anyone working with me should understand these at a high level, because they’re the building blocks we reuse the most and the glue that holds our systems together.

1) Interfaces Over Implementations

• Define contracts first. APIs, service methods, or ports describe what the system does—not how.
• Swapability. When vendors, frameworks, or tools change, we replace the adapter, not the whole system.
• Pattern: Ports & Adapters (Hexagonal Architecture).

Takeaway: Think in terms of capabilities (payments, storage, email) rather than vendor-specific code.

2) Context & Factories

• Context objects carry identity, tenant, roles, and environment.
• Factories use that context to create the right DB client, service, or adapter.
• Ensures everything is scoped and isolated, especially in multi-tenant systems.

Takeaway: Build once, use everywhere—factories prevent mistakes and maximize reuse.

3) Repositories & Services

• Repositories: Safe, tenant-aware data access (queries wrapped, no raw SQL leaks).
• Services: Business rules, validation, pricing, workflows.
• Keeps separation of concerns: data logic vs. domain logic.

Takeaway: Clear layers reduce duplication and make testing easier.

4) Idempotency & Reliability

• Idempotency keys: Prevent double charges or duplicate records.
• Retry with backoff: Handle transient errors gracefully.
• Outbox/In-box pattern: Ensure reliable delivery in event-driven flows.
• Saga pattern: Manage multi-step processes with compensation.

Takeaway: Systems should survive retries, crashes, and network hiccups without breaking.

5) Tenant Isolation & Multi-Tenancy

• Tenant context always in scope.
• Shared DB (row-level security) for efficiency.
• Dedicated schema/DB for large or regulated customers.
• Feature flags per tenant for safe rollout.

Takeaway: One app, many customers—each in their own safe bubble.

6) Security by Habit

• Principle of least privilege: Give systems and users only what they need.
• Secrets management: Keys in vaults, never in code or logs.
• Audit trails: Who did what, when, and where.
• Progressive hardening: Start safe, add MFA, BYOK, egress controls as risk grows.

Takeaway: Security isn’t a feature—it’s the default posture.

7) Observability & Feedback Loops

• Structured logs (with tenantId, userId, requestId).
• Metrics: latency, error rate, throughput, saturation.
• Tracing: follow requests across services.
• Dashboards & alerts: measure user impact, not noise.

Takeaway: You can’t fix what you can’t see. Instrument everything.

8) Data & API Patterns

• Schema validation: validate at edges (inputs/outputs).
• DTOs & mappers: decouple internal models from external contracts.
• Pagination: consistent (cursor preferred).
• Soft deletes + versioning: safer than destructive deletes.

Takeaway: Treat data as a contract—stable, explicit, and versioned.

9) Front-End & UX Patterns

• Headless components: logic in hooks/controllers; UI in small components.
• State boundaries: remote (server cache) vs. local (UI-only).
• URL as state: filters, search, pagination.
• Design tokens: shared spacing, colors, typography for consistency.

Takeaway: Frontend code should be modular, testable, and reusable across projects.

10) Workflow & Content Patterns

• Schema-driven forms: define once, render anywhere.
• Content-relations model: articles, events, companies linked predictably.
• Seed scripts: idempotent data population for dev/stage/prod.
• Issue templates: consistency in planning and acceptance criteria.

Takeaway: Build tools that reduce manual work and enforce consistency.

11) Testing & Quality

• Unit tests: validate small functions.
• Contract tests: guarantee external APIs behave as expected.
• Integration tests: check flows across services.
• Fixtures: realistic data seeds for repeatable runs.

Takeaway: Testing is less about coverage, more about confidence.

12) Documentation & Naming

• One doc per capability: what it does, inputs/outputs, failure modes.
• Consistent naming: ports = nouns (Payments), methods = verbs (charge, refund).
• Diagrams: flows (booking, checkout, refund, etc.) should be visualized.

Takeaway: Shared language makes scaling teams possible.

13) What We Reuse the Most

• Tenant context + factories
• Schema-driven forms & pricing engines
• Webhook gateway (verified, idempotent, tenant-routed)
• Upload pipeline (typed, scanned, signed URLs)
• Content + relationships (articles/events/companies)
• Audit & telemetry (same patterns everywhere)

These aren’t one-off hacks—they’re patterns we keep returning to, because they solve the same problems across projects.

Final Thought

Reusable patterns = shared wisdom.
The more we align on these principles, the less time we waste reinventing solutions.
The goal isn’t just to build software—it’s to build a culture of software that’s reliable, adaptable, and understandable to anyone joining the team.