To send real-time event notifications from a SaaS app, you usually need two parts:

1. Detect the event in your app
2. Push it immediately to the right users/systems

Here are the most common approaches, from simplest to most scalable:

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1) Webhooks for external systems

If you want to notify other apps when something happens in your SaaS:

• Your app detects an event, e.g. invoice.paid
• You send an HTTP POST to the customer’s configured webhook URL
• Include the event payload as JSON

Good for

• Integrations
• B2B notifications
• CRM, Slack, Zapier, custom listeners

Best practices

• Sign payloads with an HMAC secret
• Retry on failures with backoff
• Make delivery idempotent
• Store event IDs so you don’t send duplicates

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2) WebSockets for live UI updates

If you want users inside your app to see updates instantly:

• Open a persistent WebSocket connection from browser/mobile app to your backend
• When an event occurs, your backend pushes it to connected clients

Good for

• Dashboards
• Chat
• Collaborative editing
• Live activity feeds

Best practices

• Authenticate the socket connection
• Use rooms/channels per tenant/user
• Reconnect automatically
• Handle missed events with a fallback fetch

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3) Server-Sent Events (SSE)

If you only need server → client updates over HTTP and don’t need bi-directional messaging:

• Client opens an SSE stream
• Server sends event messages as they occur

Good for

• Simple live feeds
• Notifications
• Status updates

Pros

• Simpler than WebSockets
• Works well over HTTP
• Easy to implement in many cases

Cons

• One-way only
• Less flexible than WebSockets

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4) Message queue + notification worker

For reliable real-time delivery at scale, use an internal event pipeline:

• App writes event to DB and/or publishes to a queue
• A worker consumes the event
• Worker delivers via WebSocket, SSE, webhook, email, push, etc.

Common tools:

• Redis Pub/Sub / Streams
• RabbitMQ
• Kafka
• AWS SNS/SQS
• Google Pub/Sub

Good for

• High volume
• Guaranteed processing
• Fan-out to multiple channels
• Decoupling your app from delivery logic

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A solid architecture

A common SaaS pattern is:

1. Business action happens
   Example: user uploads a file, payment succeeds, ticket is assigned

2. Create an internal event Example: { type: "file.uploaded", tenant_id: "...", user_id: "..." }

3. Store event or publish to queue

   • Persist in DB for durability
   • Send to event bus/queue

4. Notification service consumes event

   • Determines recipients
   • Checks preferences
   • Formats payload

5. Deliver via channel

   • WebSocket/SSE for in-app real-time
   • Webhook for external consumers
   • Email/push if needed

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Recommended design choices

If your goal is in-app real-time updates

Use:

• WebSockets if you need two-way interaction
• SSE if you only need live updates from server to client

If your goal is external integrations

Use:

• Webhooks
• Add retries, signing, and event logs

If your goal is reliability and scale

Use:

• Event queue/stream + workers
• Possibly combine with WebSockets/webhooks

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Important things to get right

1. Event IDs and idempotency

Every event should have a unique ID like evt_123.
Recipients should be able to ignore duplicates.

2. Delivery retries

Network calls fail. Retry with:

• exponential backoff
• max retry count
• dead-letter queue for failures

3. User/tenant routing

Make sure events are scoped correctly:

• by tenant
• by project
• by user role
• by subscription preferences

4. Security

• Authenticate clients
• Sign webhooks
• Avoid exposing sensitive data in notifications
• Encrypt secrets

5. Observability

Track:

• event created
• event delivered
• delivery failed
• retry attempts
• latency

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Example event flow

Suppose a user comments on a document:

• Backend creates event: comment.created
• Notification service sees who subscribed
• Pushes live update to browser via WebSocket
• Sends webhook to any external integrations
• Logs delivery status

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Simple implementation stack

A practical stack might be:

• Backend API: Node.js / Python / Go / Ruby
• Event bus: Redis Streams, RabbitMQ, Kafka, or SQS/SNS
• Realtime to browser: WebSockets or SSE
• Webhooks: background worker
• Persistence: PostgreSQL table of events + delivery records

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If you want the shortest recommendation

For most SaaS apps:

• Use internal events
• Put them on a queue
• Deliver to browsers with WebSockets
• Deliver to external systems with webhooks
• Keep a delivery log and retry policy

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If you want, I can also give you:

1. a reference architecture diagram,
2. a Node.js example, or
3. a PostgreSQL schema for events + notifications.