Fastly

REST API at api.fastly.com with clean resource model. Service configuration uses a version-based workflow: clone current version, modify, validate, activate. This is more complex than Cloudflare's API-immediate model but prevents configuration errors from going live without validation. Cache purge is the star endpoint: POST to /service/{service_id}/purge/{surrogate_key} or /purge/{url} with near-instant global propagation. Real-time stats API returns per-second metrics for hit rate, bandwidth, errors, and request counts. The Stats API supports historical queries with time-range filtering. Domain and backend management follow standard CRUD patterns. VCL snippet management enables custom edge logic. Edge Dictionaries provide key-value stores updatable via API without version activation.

Fastly is a developer-oriented CDN with strong API-first design. For agents, the most valuable capabilities are instant cache purge (by URL, surrogate key, or full service — 150ms global purge), real-time stats API (per-second metrics), and edge compute via Compute@Edge (Wasm-based, supports Rust, Go, JavaScript). The REST API covers service configuration, domain management, backend configuration, and VCL (Varnish Configuration Language) deployment. Agents managing content delivery can purge specific URLs or surrogate key groups programmatically when content changes. Real-time log streaming sends access logs to configurable destinations (S3, GCS, Datadog, etc.) for agent analysis. The main barrier: Fastly's configuration model is version-based (draft → activate), adding a deployment step that simpler CDNs skip.

API tokens are created in the Fastly control panel with configurable scopes: global (full access), purge_select (purge specific URLs/keys), purge_all, and service-specific access. This scoping is more granular than many CDN APIs — agents can have tokens that can only purge, or only access specific services. Tokens are passed via Fastly-Key header. Token expiry can be set at creation time. No OAuth for third-party integrations. For agents, creating a purge-only token for cache invalidation workflows is the recommended pattern — minimal permissions for the task. Automation tokens (for CI/CD) support the same scoping. TLS for all API calls. No IP-based restrictions on tokens.

API errors return JSON with msg and detail fields. Standard HTTP status codes. Rate limits vary by endpoint: purge endpoints are generous (soft limits around 2000 purges/second per service), configuration endpoints are tighter. 429 responses include Retry-After. The version-based configuration model means activation failures return specific validation errors — agents can check configuration validity before activating. Compute@Edge errors surface in the service's log stream. Real-time stats have a ~1-second delay. The main operational consideration: VCL errors can cause service-wide outages if a bad configuration is activated. Agents managing Fastly should validate configurations and use the diff endpoint before activation. Edge dictionary updates are eventually consistent across POPs (typically < 10 seconds).

Documentation at docs.fastly.com is well-written and organized by product area (CDN, Compute, Observability, Security). API reference is comprehensive with endpoint descriptions, parameters, and curl examples. The VCL documentation is deep but VCL itself is a niche skill — Compute@Edge (Wasm) is the modern alternative. Fastly Developer Hub includes tutorials, guides, and a Fiddle environment for testing VCL. Client libraries: official CLI (fastly), community SDKs for Go, Ruby, Python, Perl, and PHP. The documentation balances conceptual explanations with practical API mechanics well. Fastly's community is developer-focused — the company invests in technical content and conference talks. For agents, the purge API and real-time stats API docs are the highest-value starting points.