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    Payment & Billing Platform

    A billing architecture that does not double-charge. Stripe is the card vault; Postgres is the invoice ledger; Redis holds idempotency keys and webhook locks. Dunning, seats, usage meters, and tax are first-class — not a weekend webhook script.

    500 – 100Kusers supported
    $120 – $1,200/month infrastructure

    Architecture Diagram

    Interactive — hover over any node to see its role and description.

    CustomerApp APIStripeBillingWebhookSignedRedisIdempotencyLedgerPostgreSQLEntitlementsUserAPIExternalBackendCacheDatabase

    Use Cases

    SaaS subscriptions with trials and seat changes
    Usage-based billing (API calls, tokens, storage)
    Marketplaces that split funds (see also Stripe Connect)
    One-time checkout with reliable fulfilment
    Internal finance exports that match Stripe to the cent

    Technology Stack

    frontend

    Next.jsStripe.js

    backend

    Node.js or Laravel Cashierworkers

    database

    PostgreSQLRedis

    infrastructure

    AWSHTTPS webhooks

    integrations

    Stripe Billingtax / invoicing

    Scalability Roadmap

    Stage 10 – 1K users· Cashier + webhooks

    Laravel Cashier or raw Stripe. One webhook endpoint. Redis for event ids.

    Stage 21K – 20K users· Metering workers

    Usage flushed on a schedule. Dunning emails. Seat sync.

    Stage 320K – 100K users· Ledger service

    Dedicated billing service. Nightly Stripe reconciliation job.

    Stage 4100K+ users· Regional Stripe + ledger

    Legal entities per region. Webhooks per account. Redis locks stay local.

    Cost Breakdown

    Development Cost

    $10,000 – $28,000 (6–14 weeks)

    Infrastructure Cost

    $120 – $1,200/month plus Stripe fees

    Maintenance Cost

    $1,200 – $4,000/month for tax, dunning, and finance ops

    Security Considerations

    Webhook secret rotation; ignore unsigned events
    Idempotency on every money mutation
    PCI: no card storage, no logs of PAN
    Finance exports are read-only replicas

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    Pin users to a region, keep Redis local, replicate the DB

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