Strimz
Concepts

How Strimz fits together

A 90-second tour of the six processes and what each one does.

Strimz runs as six processes. You only ever call one of them directly, the API. Knowing what the other five do is mostly useful when something breaks and you need to pick the right log file.

Architecture at a glance

                ┌──────────────┐
                │   apps/web   │  Marketing · Dashboard · Hosted checkout · Docs
                └──────┬───────┘
                       │ HTTPS
                ┌──────▼───────┐
                │   apps/api   │  Nest + Fastify · Privy auth · OpenAPI 3.1
                └──┬───────┬───┘
                   │       │
        ┌──────────┘       └──────────┐
        ▼                              ▼
 ┌─────────────┐               ┌──────────────┐
 │ Postgres    │               │     Redis    │
 │  (data)     │               │   (queues)   │
 └──────┬──────┘               └───────┬──────┘
        │                              │
        ▼                              ▼
 ┌─────────────┐               ┌──────────────┐
 │   indexer   │               │   scheduler  │
 │   (Go)      │  ◀──Arc RPC──▶│  (Nest+BullMQ)
 └─────────────┘               │  cron+webhook│
        ▲                      └───────┬──────┘
        │                              │
        │           ┌──────────────────┘
        │           ▼
        │    ┌──────────────┐
        └────│    agent     │  Background AI worker
             │ (Nest+cron)  │  Read-only · emails · CCTP routing
             └──────────────┘

Requests hit apps/api. It writes to Postgres and pushes background work onto Redis. When a payer submits an EIP-3009 or EIP-2612 signature, the relayer module inside apps/api signs and broadcasts the on-chain transaction with a KMS-managed key. The scheduler runs the cron side of the system: subscription charges, retry sweeps, and the webhook delivery queue. The indexer watches Arc and writes the events it sees back to Postgres. The agent reads from Postgres but never signs anything.

The six processes

apps/api

Nest + Fastify. Validates input with Zod, writes to Postgres, fires events. Also hosts the relayer that broadcasts payer-signed meta-transactions. The relayer's key is held by a KMS provider; the API process never sees raw bytes.

apps/indexer

Go process polling Arc RPC. Decodes contract events, projects them into Postgres tables. Re-derives state from chain history.

apps/scheduler

Nest + BullMQ. Runs cron jobs (subscription charges and retry sweeps) and the webhook delivery queue. On startup it decrypts the webhook signing secrets out of Postgres so the delivery worker can read them from Redis.

apps/agent

The AutoPay Agent. Hourly + daily crons. Recovery emails, cashflow digests, anomaly detection, CCTP routing. Holds no key.

apps/web

Next.js. Marketing site, merchant dashboard, hosted checkout, public storefronts, and these docs all live in the same app.

packages/contracts

Foundry workspace. Payments and Subscriptions are immutable. Registry, FeeCollector, and TokenWhitelist are UUPS-upgradeable. Every contract uses ERC-7201 namespaced storage.

Repository layout

Where to look when something is wrong

Each process owns a well-defined slice of behaviour. Knowing which slice covers the symptom is usually enough to pick the right log.

SymptomProcess to check
API returning 5xxapps/api logs
Subscriptions not charging on scheduleapps/scheduler (sweeper tick + worker)
Webhooks failing or stuck retryingapps/scheduler (delivery worker)
New on-chain payment not in dashboardapps/indexer (cursor caught up?)
Merchant not getting daily digestapps/agent (cashflow cron logs)
CCTP bridge stuck in bridge_initiatedapps/agent (Circle attestation poller)

What you don't need to think about

Built-in guarantees

  • On-chain idempotency. The contract's usedAttempts[id] mapping makes every charge attempt safe to retry without duplication. - Webhook delivery retries. The scheduler retries on a backoff schedule of 1m, 5m, 30m, 2h, and 12h. If all five attempts fail, you get an email and the endpoint can auto-disable. - Reorg protection. The indexer waits CONFIRMATIONS blocks (default 5) before projecting an event. Arc's finality makes short reorgs unlikely; the margin is there anyway.

Want to dig deeper?

Resources

The objects you'll interact with: what they mean, when they exist, what their lifecycles look like.

Idempotency

How Strimz keeps retries safe at every layer: the API, the scheduler, and the contracts.

On-chain architecture

The contract suite. What's immutable, what's upgradeable, why we drew the line where we did, and how to verify the deployment yourself.

Modes of failure

What can go wrong, what you'll see when it does, and what Strimz does about it automatically.

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