Recommendation
Keep the current backend stack. The workload is IO-heavy: accept webhook payloads, normalize fields, write durable records, fan out alerts, and keep realtime operators in sync.
A rewrite to Go, Rust, Elixir, or a managed event platform would add operational risk before it solves a measured bottleneck. The existing Node/NestJS stack is good enough for the target as long as the slow external calls stay outside the hot ingestion path.
- NestJS gives clear module boundaries for auth, leads, content, notifications, integrations, and workers.
- PostgreSQL is the correct system of record for leads, audit logs, routing rules, teams, and delivery history.
- Knex keeps SQL explicit without adding a large ORM migration surface.
- Redis plus BullMQ is the right local queue/timer layer for SLA checks, retries, and future notification jobs.
- Socket.IO is appropriate for the live operations dashboard and presence count.
Production improvement before scale
The main backend improvement should be queueing outbound notification and CRM delivery attempts. Today lead ingestion returns fast because external sends are fire-and-forget, but those attempts still execute from the API process.
For higher reliability, create BullMQ jobs for email, chat, Telegram, CRM webhooks, and spreadsheet/CRM exports. The API should insert the lead, enqueue jobs, broadcast realtime state, and return.
- Add an outbound delivery queue with exponential backoff and dead-letter state.
- Add a retry worker that scans due `next_retry_at` delivery rows.
- Add provider-specific timeouts so a slow CRM cannot tie up Node fetch calls.
- Add idempotency keys per lead/destination to prevent duplicate CRM records.
- Add load tests around `POST /webhooks/capture` before claiming the `<200ms` target under traffic.