# Autonomous Backend Architecture & API Intelligence

Webdev Agent OS v28 governs the backend as an evidence-linked system of domain ownership, request contracts, data authority, transaction behavior, asynchronous delivery, authorization, abuse controls, caching, scalability, and controlled evolution.

## Purpose

Backend code is not considered well architected merely because endpoints respond. The system must be able to explain:

- Which service owns each domain responsibility.
- Which API contract exposes that responsibility.
- Which data store is authoritative.
- Where transaction boundaries begin and end.
- How background jobs retry, fail, and recover.
- Which authentication and authorization policy protects each capability.
- How abuse and traffic pressure are bounded.
- What consistency and invalidation guarantees caches provide.
- Which runtime budgets prove the service can meet expected demand.
- Which change proposal, evidence, reviewer, and rollback plan govern evolution.

## Evidence chain

```text
Product requirement
→ Domain service
→ API contract
→ Data ownership
→ Transaction or queue boundary
→ Authentication and authorization policy
→ Rate limit and cache policy
→ Scalability budget
→ Dependency and blast radius
→ Verified release and runtime evidence
```

## Core records

### Services

A service record defines its domain, owner, source location, requirements, and operational role. The implementation supports edge, domain, application, worker, integration, read-model, and similar boundaries without forcing premature microservices.

### API contracts

Contracts include method, path, version, request and response schema references, consumers, test evidence, and status. A verified contract requires response schemas and test evidence.

### Data stores and transactions

Each data store has one accountable owner service. Transaction records identify participating services and stores, consistency strategy, rollback evidence, and verification status.

### Queues and background work

Queues require producers, consumers, retry limits, delivery guarantees, and dead-letter handling. Missing retry or failure evidence is treated as risk.

### Access and abuse controls

Authentication, authorization, tenant scope, capability boundaries, rate limits, and abuse tests are first-class architecture evidence rather than middleware assumptions.

### Caching and consistency

Cache policies record TTL, key dimensions, invalidation, and consistency expectations. Persistent personal identifiers are rejected as cache-key evidence.

### Scalability budgets

Budgets can govern latency, throughput, queue lag, database connections, resource consumption, or other measurable backend constraints. A budget cannot pass when its measured value violates its configured limit.

### Service dependencies

Dependency records preserve synchronous versus asynchronous behavior, criticality, timeout, circuit-breaker evidence, and blast radius. New synchronous dependency cycles are rejected.

### Evolution proposals

Consequential backend changes require verification evidence, rollback instructions, and independent approval. Proposal authors cannot approve their own work.

## Illustrative v27 baseline

- 7 services
- 12 API contracts
- 6 owned data stores
- 5 transaction boundaries
- 5 queues
- 6 authentication and authorization policies
- 5 rate-limit policies
- 5 cache policies
- 8 scalability budgets
- 11 service dependencies
- 3 open duplicate business-logic records
- 3 architecture options
- 3 evolution proposals
- 63/100 backend architecture health

The baseline intentionally retains a failed tenant-scope contract, two failed scalability budgets, one pending rate limit, one pending cache policy, and duplicate business logic.

## External-system boundary

The included records do not claim that GitHub, a database, queue provider, identity provider, API gateway, observability platform, cloud environment, or production deployment is connected. Connector evidence must remain explicit and independently verifiable.