# API Gateway Mapping for GIS Services

The ingress control plane that translates external consumer requests into domain-routed spatial workloads inside the federated mesh.

In an enterprise geospatial platform, the API gateway is the single point where untrusted external traffic meets the internal estate of vector engines, raster tile servers, and geocoding resolvers — each owned by a different team and bound by a different contract. Mapping those services correctly is the difference between a predictable, observable routing fabric and a brittle proxy that leaks failures across domain boundaries. This page sits within the Federated Ownership & Routing Architecture, and it frames the gateway not as a monolithic reverse proxy but as a declarative routing surface that enforces ownership, validates spatial contracts at the edge, and degrades gracefully under load. It is closely coupled to the Cross-Domain Routing Strategies that govern how requests fan out once a domain has been resolved.

Figure — The gateway authenticates and validates once, then fans requests out to the owning vector, raster, or geocoding backend.

# Architectural Boundaries & Design Rationale

The gateway exists to enforce a hard boundary between the request’s intent and the domain’s execution. Vector rendering pipelines, raster processing queues, and geocoding resolution engines must operate inside dedicated failure domains so that a saturated mosaicking queue cannot exhaust the connection pool serving feature queries. By decoupling ingress routing from compute execution, the gateway preserves the integrity of the broader mesh and keeps each domain’s performance envelope independent. Ownership boundaries are codified through namespace-scoped route tables, tenant-aware rate limits, and explicit service-mesh egress policies, mapping the same domain ownership model that drives Spatial Domain Boundary Design down onto the routing layer.

Treating the gateway as a federated routing fabric prevents three recurring failure modes. First, lateral traversal: without explicit allow-listing of inter-service paths, a compromised consumer token can pivot from a geocoding endpoint into a cadastral feature store. Second, cross-domain contamination: shared route tables let a misconfigured raster route shadow a vector prefix, silently misdirecting traffic. Third, unbounded fan-out: a request that resolves to multiple regional tile caches without a circuit breaker turns a single slow shard into a platform-wide latency spike. The gateway closes all three by evaluating tenant isolation, path ownership, and health-aware precedence before any payload reaches a backend.

Routing precedence follows a strict evaluation order so that resolution is deterministic and auditable:

1. Tenant isolation headers (X-Tenant-ID, X-Spatial-Context)
2. Path prefix matching (/api/v1/vector, /api/v1/raster, /api/v1/geocode)
3. Query parameter routing (?crs=EPSG:4326, &format=geojson)
4. Default fallback with explicit 404 or 503 based on service health

The gateway should evaluate spatial bounding-box metadata early in this lifecycle. Pre-flight validation of bbox parameters enables intelligent dispatch to regional tile caches, distributed spatial databases, or edge-optimized rendering nodes — and rejects out-of-bounds requests before they consume backend capacity. When routing across federated domains, topology changes must propagate through event-driven signals rather than polling, which is why this layer integrates the Domain Sync Protocols for Spatial Data so that route tables, cache-invalidation signals, and tenant entitlements move atomically across the mesh.

# Specification & Contract Reference

Every route the gateway exposes is governed by an explicit contract: the headers it requires, the spatial parameters it validates, and the failure semantics it guarantees. The following surface is the minimum the GIS ingress layer enforces before a request crosses a domain boundary.

Contract validation happens at the edge, before payloads traverse internal service boundaries. Middleware enforces strict JSON Schema validation for OGC API Features responses, GeoJSON geometry compliance, and protobuf-encoded tile payloads, intercepting malformed coordinates, invalid EPSG codes, and out-of-bounds tile requests with standardized 422 responses carrying machine-readable diagnostics. These checks are not duplicated guesswork — they reference the same versioned definitions enforced by Schema Contracts for Vector/Tile Data, so a geometry that passes producer-side CI also passes at the gateway. Transformation rules are compiled into declarative policies that strip sensitive metadata (PII, internal tracking IDs), normalize timestamps to ISO 8601 UTC, inject the tenant-scoped X-Spatial-Partition-Key, and enforce geometry validity before the request is routed.

# Production Implementation

The gateway is configured declaratively and managed through GitOps so that routing manifests are versioned alongside the spatial data contracts they enforce. The example below is a runnable Kubernetes Gateway API definition that binds a vector ingress route to schema validation, then a second manifest that routes a heavy asynchronous spatial-join workload with idempotency and strict timeout boundaries. Both call out the zero-trust and idempotency requirements explicitly.

# Vector ingress: validate the GeoJSON contract at the edge before backend dispatch.
# Zero-trust: this route only resolves after the gateway has terminated mTLS and
# verified the tenant JWT — see the security listener on the parent Gateway.
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: vector-ingress-validation
spec:
  parentRefs:
    - name: geospatial-gateway
  rules:
    - matches:
        - path:
            type: PathPrefix
            value: /api/v1/vector
      filters:
        - type: ExtensionRef          # delegate contract checks to the schema validator
          extensionRef:
            group: validation.mesh.io
            kind: SchemaValidator
            name: geojson-contract-v2  # versioned, mirrors the producer-side CI schema
      backendRefs:
        - name: wfs-feature-engine
          port: 8080

Heavy spatial queries — spatial joins, network-routing calculations, and large-scale raster mosaicking — must never block the request thread. The gateway acts as a request broker: it validates, stamps a deterministic idempotency key, and returns 202 Accepted with a job URI while async workers consume from domain-scoped queues. Idempotency is mandatory here, because a retried submission must not enqueue a second multi-minute mosaicking job.

# Async spatial-join route. Idempotency-Key promoted to an internal header so the
# broker can deduplicate replays within the 300s TTL window; strict timeouts stop a
# slow backend from exhausting the gateway connection pool.
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: async-spatial-workflow
  annotations:
    mesh.io/idempotency-ttl: "300s"   # replays inside this window return the original job
    mesh.io/async-mode: "true"
spec:
  parentRefs:
    - name: geospatial-gateway
  rules:
    - matches:
        - path:
            type: PathPrefix
            value: /api/v1/jobs/spatial-join
      filters:
        - type: RequestHeaderModifier
          requestHeaderModifier:
            set:
              - name: X-Idempotency-Key
                value: "from-header:Idempotency-Key"
              - name: X-Security-Policy
                value: "strict-spatial"   # WAF profile blocking spatial-function injection
        - type: URLRewrite
          urlRewrite:
            path:
              type: ReplaceFullPath
              value: /internal/async/submit
      backendRefs:
        - name: spatial-job-broker
          port: 8443
      timeouts:
        request: "5s"
        backendRequest: "2s"

The submission, execution, and completion phases stay strictly separated. On submission the gateway validates the payload, generates an X-Request-Trace-ID, and returns 202 Accepted with a job URI. During execution, async workers consume from Kafka or RabbitMQ topics with exponential backoff retry policies. On completion, results are persisted to object storage or spatial databases and the gateway proxies status checks via /jobs/{id}. This broker pattern is the ingress contract for the Async Execution for Heavy Spatial Queries backends, which own the queue topology and worker scaling behind it. Validating that these manifests resolve to the correct distributed endpoints is covered in detail in Mapping API gateways to distributed GIS endpoints.

Security enforcement at this layer is zero-trust by default. All ingress traffic requires mutual TLS termination, JWT validation against domain-scoped OIDC providers, and spatial rate limiting based on tenant quotas. WAF rules explicitly block SQL/NoSQL injection patterns targeting spatial functions such as ST_Intersects and ST_DWithin, and restrict coordinate precision to prevent payload-amplification attacks where an attacker inflates geometry vertex counts to exhaust parser memory.

# Diagnostic Runbook

When a spatial route misbehaves, the failure is almost always in header propagation, contract validation, registry sync, or a tripped circuit breaker — not the network. Work the steps in order; each one isolates one boundary the gateway enforces.

1. Recover the trace. Read X-Request-Trace-ID from the client response headers and query the distributed tracing backend for the gateway span duration and the downstream latency breakdown. A missing trace ID means the request never passed ingress validation — jump to step 3.
2. Confirm header propagation. Verify that X-Tenant-ID and X-Spatial-Context survived the proxy hop. A dropped tenant header collapses precedence to the default route and surfaces as a spurious 404 or a cross-tenant data leak.
3. Inspect validation middleware. Search the validator logs for schema_mismatch or crs_unsupported tags. These pinpoint a contract drift between the producer schema and the edge schema version pinned in the route.
4. Check policy evaluation. Review the WAF/policy decision log for strict-spatial denials. Injection-pattern blocks and precision-cap rejections both appear here before the backend is ever contacted.
5. Validate rate-limit and breaker state. Read the tenant rate-limit counters and circuit-breaker states in the gateway control plane. A breaker stuck open routes every request to the fallback path.
6. Verify artifact and route integrity. Confirm the deployed HTTPRoute revision matches the Git SHA in source control; a partial GitOps apply leaves stale backendRefs pointing at a retired service port.
7. Refresh topology on suspected desync. If routing-table desync is suspected, trigger a forced topology refresh via the domain sync controller and re-run step 1 to confirm the corrected route resolves.

When primary geocoding resolvers exceed latency SLOs or return 5xx, traffic must shift to secondary providers or cached approximate matches rather than failing the client. That health-aware degradation is governed by the Fallback Chains for Geocoding Services pattern, which the gateway invokes as the last tier of its precedence chain.

# SLA Targets & Performance Baselines

The gateway carries thin, predictable overhead; the heavy work belongs to the domains behind it. The targets below are the budget the ingress layer must hold so that domain SLAs remain meaningful.

Holding these baselines relies on geographic affinity routing, HTTP/2 connection multiplexing, and edge caching for tile-matrix metadata. Cache invalidation must stay event-driven, triggered by domain-ownership registry updates or schema-contract version bumps rather than fixed expiry, so that a stale route is corrected within the sync-drift budget above.

# Governance & Compliance Notes

Routing decisions are governance decisions, so the gateway treats them as auditable artifacts. Every route manifest is policy-as-code: schema validators, WAF profiles, and tenant rate limits are committed to source control, reviewed, and promoted only after a CI pipeline validates schema compliance, tests idempotency replay behavior, and simulates circuit-breaker thresholds. This keeps the ingress contract aligned with the catalog records described in Metadata Cataloging for Raster/Vector, so a consumer-visible route maps to a governed, documented data product.

Audit requirements are concrete. The gateway captures routing decisions, schema-validation failures, and idempotency cache hits in append-only, tenant-partitioned streams, and injects W3C Trace-Context plus OpenTelemetry baggage at ingress so every decision can be correlated with downstream spatial-engine logs. Structured error envelopes return a consistent error_code, trace_id, retry_after, and diagnostic_hint for every 4xx/5xx, giving compliance reviewers a deterministic record. Where jurisdictional constraints apply — data-residency rules that bind a tenant’s vector features to a specific region — the gateway enforces them at precedence tier 1, refusing to route a request whose bbox or tenant context falls outside the permitted extent. Health probes (/ready for dependency checks, /live for process liveness) carry spatial-specific validations such as tile-cache connectivity and CRS-registry availability, so a degraded compliance dependency surfaces before it serves a non-compliant response.

# Related

• Up to the parent: Federated Ownership & Routing Architecture
• Cross-Domain Routing Strategies — how requests fan out once a domain is resolved
• Schema Contracts for Vector/Tile Data — the versioned definitions enforced at the edge
• Async Execution for Heavy Spatial Queries — the broker backends behind the async routes
• Mapping API gateways to distributed GIS endpoints — validating route-to-endpoint resolution