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Design clear service contracts
Define resources, operations, schemas, status codes, pagination, error formats, versioning, idempotency, and compatibility rules before implementation.
Server-side engineering workflow
CategorySoftware Development
Codex Skills for Backend Development
Codex Skills for Backend Development give Codex structured instructions for designing APIs, modeling data, implementing business rules, securing access, handling failures, testing services, and preparing systems for production. Download the skills and adapt them to your framework, database, infrastructure, and service boundaries.
API designData modelingSecurityObservability
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task: build order service
inspect:
- domain rules
- data consistency
- failure paths
verify: tests + logs + contractThe happy path is only the beginning
Backend code must stay correct when requests repeat, dependencies fail, and several users change the same data.
A useful backend does more than return JSON. It protects resources, enforces domain rules, manages transactions, validates inputs, preserves compatibility, records important events, and fails in ways operators can understand.
These skills guide Codex through server-side architecture, REST API development, database integration, authentication, caching, queues, testing, and deployment readiness without hiding important tradeoffs.
What the downloadable skills can do
What Codex Skills for Backend Development can help build
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Model reliable data flows
Design tables and indexes, choose transaction boundaries, plan migrations, validate joins, prevent duplicate work, and handle concurrent updates.
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Protect every boundary
Apply authentication, resource-level authorization, typed validation, secret handling, rate controls, safe logging, and tests for denied access.
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Prepare for real operations
Add structured logs, metrics, traces, health checks, timeouts, retries, graceful shutdown, runbooks, and useful failure responses.
From domain rule to running service
Build around contracts, invariants, and failure behavior
The process starts with the business rule and trust boundary, then carries those decisions through storage, code, tests, and production signals.
workflow.statusREADY
Context → Plan → Work → Verify
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Map the domain and constraints
Identify actors, permissions, entities, invariants, workflows, consistency needs, expected load, sensitive data, and external dependencies.
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Define contracts and storage
Specify request and response schemas, error behavior, persistence model, indexes, migrations, transaction scope, and ownership boundaries.
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Implement the complete path
Build validation, authorization, business logic, persistence, dependency calls, observability, and predictable error handling.
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Prove production readiness
Run unit, integration, contract, migration, security, concurrency, and failure tests, then document deployment and rollback.
Fits established backend stacks
Keep engineering standards consistent across languages and frameworks
The skill follows the repository's architecture instead of forcing one framework onto every service.
Node.js and TypeScript
Build typed services, middleware, background jobs, database access, validation, tests, and asynchronous network workflows.
Python services
Develop APIs, workers, data access layers, validation, dependency management, and testable application boundaries.
.NET backends
Create ASP.NET Core APIs, services, EF Core persistence, authentication policies, background work, and automated tests.
JVM services
Work with Spring-style applications, typed domains, persistence, transactions, messaging, configuration, and service tests.
Common server-side work
Use the skills from first endpoint to production incident prevention
Each workflow can cover a new service, an existing backend, or one risky change inside a mature system.
01Design a REST or RPC API
02Create database schemas and migrations
03Implement authentication and authorization
04Add queues and background workers
05Prevent duplicate request processing
06Improve caching and query performance
07Write integration and contract tests
08Add logs, metrics, and health checks
Teams responsible for system behavior
Who Is This For?
These skills are for people who need backend changes that are understandable, testable, secure, and ready to operate.
Backend developers
Build and maintain APIs, services, jobs, persistence layers, integrations, and operational controls.
Full-stack developers
Handle server-side work with explicit contracts, access rules, data integrity, and production checks.
Platform teams
Standardize service structure, telemetry, configuration, deployment health, resilience, and incident-friendly behavior.
Technical founders
Turn product requirements into a backend that can evolve without losing security or data consistency.
Good to know:
The skills assist engineering work but do not replace architecture review, threat modeling, load testing, privacy assessment, database expertise, or qualified approval for high-risk production systems.
Set up the service context
Installation Guide
Install the skills where Codex can inspect the backend code, schema, tests, configuration examples, and operational documentation.
Download and extract the backend development skills
Keep each SKILL.md file with its contract guidance, security checks, testing process, and supporting references.
Choose project or personal scope
Use project scope for one service's architecture and rules, or personal scope for a reusable backend workflow.
Document the system boundaries
Record actors, permissions, data ownership, dependencies, service contracts, sensitive fields, consistency rules, and deployment environment.
Add local verification commands
Provide approved build, test, migration, lint, security, and service-start commands plus required test dependencies.
Begin with one observable outcome
Describe the behavior, inputs, outputs, failure cases, compatibility limits, and acceptance checks before implementation.
Before you build
Frequently Asked Questions
Answers about frameworks, databases, API security, legacy systems, and production readiness.
Which backend frameworks are supported?+
The skills can adapt to frameworks already present in the repository. Supply the language, framework version, architecture, and project commands.
Can they design a database?+
They can help model entities, constraints, indexes, queries, migrations, and transactions. Important schemas still need review against real access patterns, scale, and recovery requirements.
Do they cover API security?+
Yes. The workflow includes authentication, object-level authorization, input validation, secret handling, safe errors, logging, rate controls, and abuse-focused tests.
Can they work in a legacy backend?+
Yes. They begin by tracing current behavior and constraints, then favor contained, compatible changes with regression coverage and a rollback plan.
Will the service be production-ready automatically?+
No. The skills prepare and verify many production concerns, but deployment approval still depends on your infrastructure, security, performance, compliance, and operational standards.
Build for the requests you cannot predict
Give Codex a backend workflow that protects data, handles failure, and leaves a system operators can understand.
Explicit contracts. Enforced rules. Tested failures. Useful production signals.