Architecture & components

Components

Component	What it is	Notes
API	Go service (Gin)	The product. Stateless except for its on-disk WAL.
MongoDB	Off-chain record store	The queryable hot tier.
Redis	Cache + shared rate limiter	Optional; the API degrades gracefully without it.
Hyperledger Fabric	Permissioned ledger	Stores Merkle roots; Go chaincode. External to the API.
WAL	On-disk write-ahead log	Per-pod; must be on durable storage.
Dashboard	Static web UI (nginx)	Optional; talks directly to the API.

How they connect

            ┌─────────────┐      gRPC (gateway)
  client ──▶│   Go API    │──────────────────────▶  Hyperledger Fabric
            └─────┬───┬───┘                          (Merkle roots, write-once)
                  │   └────────▶ Redis (cache + limiter)
                  ▼
              MongoDB (records)        WAL (durable record writes)

The API talks to Fabric only through the gateway gRPC SDK with an X.509 identity — no Docker socket, no peer CLI.

Statefulness & scaling

• API: mostly stateless, but the file WAL is per-pod. A ReadWriteOnce PVC cannot be shared across nodes, so multi-node HA needs a StatefulSet (per-pod WAL) — the Helm chart gates replicaCount > 1 behind an explicit opt-in.
• Rate limiting & batching are already multi-instance safe (Redis-backed limiter, atomic batch claim).
• MongoDB/Redis/Fabric scale on their own terms (replica sets, clusters, multi-org networks).

Deployment paths

• Docker Compose for a single host.
• Kubernetes (Helm) for production.