Run two or three CDNs in front of the same origin, steer traffic with simple health‑aware DNS, keep the same caching, TLS, and security rules on every provider, stream all logs to one place, watch real users, and automate purges and failover. Start tiny, ramp by region, and keep a one‑click runbook.
That gives you the uptime and latency gains of multi CDN architecture without confusing your team.
How To Plan A Multi‑CDN Strategy
Before touching settings, write down what you are trying to hit. Keep it short.
- Availability target per region, for example 99.9 percent.
- Performance target, like p95 TTFB under 600 ms for HTML.
- Budget guardrail, such as a maximum effective cost per GB.
- Scope of traffic you will put behind the multi CDN solution: HTML, static assets, APIs, video, large downloads, even dynamic assets too these days.
This plan guides every decision. If a choice does not help these numbers, skip it.
How To Choose CDN Providers
Pick two providers that cover each other’s weak spots instead of two clones. Look for different peering and strong regions that match where your users are.
Make sure both can do the boring essentials.
Two primaries plus a quiet third you can switch on is enough for most teams.
If you already use a controller like IO River to unify routing and config, keep it as the single pane of glass and avoid hand‑configuring each CDN provider one by one.
How To Configure DNS Traffic Steering
Start with managed DNS. It is simple, cheap, and vendor neutral.
- Use short TTLs, usually 20 to 60 seconds for apex and www.
- Create per‑region weights so you can shift traffic locally without moving the world.
- Add health checks that hit a real page or a small JSON API, not just “/healthz”.
Steering options include:
If you can keep it simple with DNS, do it. Keep the other methods as tools you can add later.
How To Standardize Caching For Multi‑CDN
Caching rules must match across providers or your numbers will lie. Make one caching contract and apply it everywhere.
- Cache key should include scheme, host, path, and only query params that change content. Ignore marketing params like utm_*, gclid, fbclid, ref.
- Vary headers should be short and consistent. Accept and Accept‑Encoding are usually enough for static files.
- Use Cache‑Control s‑maxage for TTLs. Add stale‑while‑revalidate so an edge can serve a response while it refreshes in the background.
- Prefer tag purge so a release can clear an entire set in one call.
How To Set Up Security And TLS Across CDNs
Security must be the same everywhere. Otherwise a failover opens a hole without warning.
- WAF rules mirrored on both providers. Same managed sets, same custom rules.
- Bot management with the same allowlists and challenge rules.
- Rate limits copied for login, checkout, search, and APIs.
- Signed URLs or signed cookies with the same token format and clock skew tolerance.
- TLS minimum version, cipher suites, HSTS, and OCSP stapling set to the same values.
- Use managed certs or ACME where possible so renewals are automatic.
I like to keep a security template and a TLS template, then render them for each platform so the intent stays identical.
How To Lock Down Origin And Origin Shielding
Protect the origin so only your chosen edges can talk to it.
- Allowlist CDN egress IPs or require mutual TLS from each provider.
- Enable origin shield on each CDN in a region close to your origin. This reduces duplicate origin hits when caches are cold.
- Serve the same hostnames on every provider. Avoid provider vanity hosts to keep cookies and CORS simple.
- If there are multiple origins, label and route them clearly so a failover does not cross streams.
This keeps origin load steady when you move traffic between providers.
How To Automate Purges In A Multi‑CDN
Purge is a top source of mistakes. Make it boring.
- Build a small service that accepts a tag or a URL list and then calls each CDN’s API.
- Trigger that service from deploys, CMS publishes, and emergency clears.
- Keep a manifest of critical URLs for the provider that only supports URL purge.
How To Monitor And Route With Data
Do not steer by vibes. Watch real users and robots, then let routing react.
- Real user monitoring. A small beacon collects provider, region, TTFB, TLS time, and errors. Sample lightly to avoid noise.
- Synthetic checks. Per region, per minute, for HTML, key APIs, and critical assets.
- Log streaming. Push edge logs from every CDN into the same sink with the same field names like provider, colo, region, status, cache_status, bytes.
How To Roll Out Multi‑CDN Safely
Ship small, observe, then increase.
- Staging parity. Each provider should serve the same staging host and origin so tests are apples to apples.
- Canary. Start with 1 to 5 percent in two or three representative regions. Watch p95 TTFB, error rate, cache hit, and origin load.
- Ramp. Move to 10 to 25 percent, then to 50 percent. Stop if KPIs slip.
- Runbook. Keep three buttons handy. Fail to A, fail to B, restore balanced.
Keep CDN configs in version control. Use templates so rules match even when provider features differ.
