Incremental Migration with the Strangler Fig Pattern: Decoupling Drupal Without Risk

Coexistence Architecture: Headless Drupal and Next.js

Single Source of Truth and Stateless Frontend

Decoupling never means data duplication or fragmentation. Drupal’s relational database remains the sole, authoritative logical source of truth (Single Source of Truth) for all editorial content, taxonomies, authorization rules, and layout configurations.

The new public presentation layer built on Next.js operates in a strictly stateless, read-only mode for public visitors. The Node.js server manages no user sessions or public authentications. We enforce a rigorous Backend For Frontend (BFF) pattern: the client browser never interacts directly with internal CMS endpoints or backend services. Every client request is routed exclusively through server-side Node.js interfaces, establishing network isolation that significantly reduces the overall attack surface.

Low-Latency Edge Routing

How do we decide whether a request should be served by the legacy system or the new frontend without degrading Time To First Byte (TTFB)?

Traffic routing is handled at the Edge by an Nginx-based proxy infrastructure extended with custom Lua modules. This proxy queries a route map synchronized in real time onto an isolated in-memory datastore.

Routing decisions are resolved at the network layer in milliseconds without ever invoking Drupal's execution cycle, protecting baseline response times.

Caching, Invalidation, and Zero Build-Time Fetching

Outbox Pattern and Event-Driven Invalidation

To maintain peak performance without serving stale data, we eliminate fixed time-based cache regeneration across the platform. We implement Stale-While-Revalidate (SWR) semantics paired with an event-driven invalidation circuit.

When an editor publishes or updates content, the CMS triggers the Outbox Pattern: the state change is recorded inside the same atomic database transaction as the editorial update. An asynchronous background process then syncs the edge routing datastore and notifies the Next.js frontend. To protect the system against unauthorized triggers, every notification is signed with an HMAC (Hash-based Message Authentication Code) cryptographic signature. Next.js validates the signature, timestamp, and event uniqueness before marking cached data as stale.

If a backend service becomes temporarily unavailable, the Node.js SDK mitigates the disruption using a Circuit Breaker mechanism, triggering explicitly defined fallback modes (degraded mode) for each functional capability.

Constant-Time CI/CD Pipelines

In an enterprise infrastructure, growing editorial content volumes must never slow down production deployments. Adopting the Zero Build-Time Fetching paradigm, our Continuous Integration (CI/CD) pipelines compile and validate the Next.js application without querying internal Drupal services. Build times remain constant and entirely decoupled from the database size.

Content hydration and page composition occur strictly at runtime upon the first user request. Production deployments utilize a high-availability Blue/Green model built on mirrored environments. Load balancers perform zero-downtime traffic switches, while observability systems constantly monitor Service Level Indicators (SLIs) — such as TTFB, LCP, and error rates — initiating automated rollbacks if performance anomalies occur.