The Realtime Playbook: How to Add Chat and Notifications to Your App

Your App Needs to Be Realtime. Here's Why.

Think about the apps you use every day. When a Slack message arrives, it appears instantly. When your DoorDash driver is approaching, you see their icon move on a map. When you get a new follower on Instagram, a notification pops up immediately. That feeling of immediacy, of your app being alive and connected to the world, is what we call "realtime."

It’s no longer a luxury feature reserved for FAANG companies. For most modern web and mobile apps, realtime functionality is table stakes. It's the difference between an app that feels dynamic and engaging, and one that feels static and dated. If you're building a SaaS platform, a marketplace, a social network, or an internal tool for a fast-moving team, you're not just competing on features—you're competing on feel. And the realtime feel is a powerful differentiator.

But as a founder or product lead, you're faced with a critical question: how do you actually build this? Do you build a custom chat system from scratch? Do you plug in a third-party service? What does it cost? How long does it take? This guide is your playbook. We're going to cut through the noise and give you the concrete information you need to make the right architectural and business decision for your product.

The Core Technology: How Realtime Actually Works

Before you can decide what to build, you need a fundamental understanding of how it works. Don't worry, you don't need a computer science degree. We'll break it down using simple analogies.

The Old Way: Polling (and Why It's Bad)

Imagine you're expecting an important letter. The old-school way to check is to walk to your mailbox every five minutes, open it, see if there's anything new, and close it. This is polling.

In technical terms, the client (your user's browser or mobile app) repeatedly sends a request to the server every few seconds asking, "Anything new for me?" Most of the time, the server says, "Nope." This is incredibly inefficient.

• It's slow: Users only get updates every few seconds, so it's not truly "realtime."
• It's wasteful: It creates a ton of unnecessary network traffic and server load.
• It doesn't scale: Imagine 10,000 users all asking "Anything new?" every five seconds. Your servers will buckle under the weight of answering "No" millions of times.

For anything other than a low-traffic dashboard with non-critical updates, polling is the wrong choice for modern realtime features.

The Modern Way: WebSockets

Now, imagine instead of walking to the mailbox, you just have an open phone line with the post office. The moment a letter arrives for you, they tell you immediately. This is a WebSocket.

A WebSocket is a persistent, two-way communication channel between the client and the server. The client opens the connection once, and it stays open. The server can then "push" data to the client the instant it's available, without waiting for the client to ask for it. This is the magic behind every modern chat app.

This approach is:

• Fast: Data transfer is nearly instantaneous.
• Efficient: No more wasted requests. The server only sends data when there's actually something new.
• Scalable: A single server can maintain thousands of open WebSocket connections with far less overhead than a polling-based system.

Technologies like Node.js, combined with libraries like Socket.IO or ws, are the standard for building custom WebSocket servers. They are purpose-built for handling this kind of asynchronous, event-driven communication.

Push Notifications: The Mobile Piece of the Puzzle

WebSockets are fantastic when your app is open. But what about when it's closed or in the background on a user's phone? You can't keep a WebSocket connection open indefinitely without draining the battery.

This is where push notifications come in. Think of this as the server having the user's pager number. Even if the phone line (WebSocket) is disconnected, the server can send a page (a push notification) to get their attention.

Your server doesn't send these directly to the user's device. Instead, it sends the notification payload to a platform service:

• Apple Push Notification Service (APNs) for iOS devices.
• Firebase Cloud Messaging (FCM) for Android devices.

These platform services then handle the complex and power-efficient delivery to the device. When the user taps the notification, it opens your app, which can then re-establish its WebSocket connection to get the full context.

The Big Decision: Build vs. Buy

This is the million-dollar question, sometimes literally. Do you invest your engineering resources in building a custom realtime backend, or do you pay a monthly fee to a service that handles it for you? There's no single right answer, but there's a right answer for you, based on your stage, budget, and long-term vision.

Option 1: Build It Yourself (The DIY Path)

Building your own realtime infrastructure means your team (or a partner studio) will be creating a dedicated service, likely using Node.js and WebSockets, to handle all realtime communication. This service will sit alongside your main application backend.

Pros:

• Total Control & Customization: You can build any feature you can imagine, tailored precisely to your business logic. You're not limited by a third-party API.
• Own Your IP: The system is a valuable asset of your company.
• Predictable Long-Term Cost: After the initial build cost, your only ongoing expense is server infrastructure, which scales more predictably than per-user SaaS pricing.
• Data Privacy: All user data and messages stay within your infrastructure.

Cons:

• High Upfront Cost & Time: This is a significant engineering project. It requires specialized backend expertise and can take months to build and stabilize.
• Maintenance Burden: You are responsible for uptime, scaling, security patches, and bug fixes. This is not a "set it and forget it" system.
• Complexity: Building a reliable, scalable realtime system is genuinely hard. There are dozens of edge cases around disconnects, message ordering, and security.

This path is best for well-funded startups who see realtime as a core, differentiating part of their product, or for companies with strict data privacy requirements. This is also where an experienced development partner like Envert provides immense value. Instead of you spending 3-6 months trying to hire a rare, specialized backend engineer, you can leverage our team's existing expertise in building robust, scalable realtime systems from day one.

Option 2: Use a Third-Party Service (The SaaS Path)

This involves integrating a managed realtime platform, often called a "Pub/Sub" (Publish/Subscribe) service. You integrate their SDK into your frontend and backend. Your backend "publishes" messages to a channel, and your frontend clients "subscribe" to that channel to receive the messages.

Popular services include Pusher (now part of MessageBird), Ably, PubNub, and for push notifications specifically, OneSignal.

Pros:

• Speed to Market: You can have a basic realtime feature up and running in days, not months. This is a massive advantage for MVPs and early-stage products.
• Low Upfront Cost: You're paying a monthly subscription instead of a large, upfront capital expense for development.
• Managed Infrastructure: They handle the scaling, uptime, and reliability. You don't get paged at 3 AM if a server goes down.

Cons:

• Scaling Costs: The pricing models are usually based on connections, messages, or monthly active users. As your app grows, these costs can balloon and become a significant line item.
• Less Flexibility: You are limited to the features and API provided by the vendor. Complex, custom logic can be difficult or impossible to implement.
• Vendor Lock-in: Migrating away from one of these services once you're deeply integrated is a major undertaking.
• Data Handling: Your data is passing through a third-party's servers, which might be a concern for certain industries.

This path is ideal for early-stage startups testing an idea, products where realtime is a nice-to-have but not core, or teams without in-house backend expertise.

The Hybrid Approach

A smart strategy for many is to start with a third-party service for your MVP to get to market quickly and validate your product. Plan from the beginning that if the product is successful, you will eventually replace the third-party service with a custom-built solution in a "V2" phase. This gives you the best of both worlds: speed now, and control and cost-effectiveness later.

A Realistic Look at Costs & Timelines

Let's put some real numbers on the table. These are ballpark figures based on working with US-based senior developers or a studio. Costs will vary based on scope, complexity, and who you hire.

Cost of Building a Custom Solution

Building a custom realtime system is a major project with two main components: the backend service and the frontend integration.

• Backend (WebSocket Server):
  • Scope: Basic 1-on-1 chat, authentication, message history.
  • Time: 4-6 weeks
  • Cost: $20,000 - $40,000
• Frontend (Web or Mobile App Integration):
  • Scope: Building the chat UI, connecting to the WebSocket server, handling state management.
  • Time: 3-5 weeks
  • Cost: $15,000 - $30,000
• V1 Total:
  • Timeline: 8-12 weeks
  • Cost: $35,000 - $70,000

Want to add group chat, typing indicators, media uploads, and push notifications? You're likely looking at a total project cost of $60,000 - $120,000+ and a timeline of 12-20 weeks.

At Envert, we've built complex realtime systems for SaaS MVPs and enterprise internal tools. A typical custom chat or notification engine MVP we build falls in the $50k-$90k range and is delivered in about 12-14 weeks, including backend, frontend, and infrastructure setup.

Cost of Using a Third-Party Service

Here, the upfront development cost is much lower, but you take on a recurring operational expense.

• Upfront Development:

  • Scope: Integrating a service like Pusher or Ably into your backend and frontend.
  • Time: 1-3 weeks
  • Cost: $5,000 - $15,000

• Ongoing Subscription Costs:

  • Pusher: Plans range from a free tier to $49/mo (100 concurrent connections, 2M messages/day) up to $499/mo and beyond. A moderately successful app could easily be paying $200-$500/month.
  • Ably: Similar pricing model, scaling with peak connections and messages. A growing app will quickly move into the multi-hundred-dollar-per-month plans.
  • OneSignal (for Push): Has a generous free tier, but paid plans with more features start at $99/mo and scale with subscribers.

The breakeven point is often around 18-24 months. If your monthly SaaS bill is $3,000, that's $36,000 a year. A custom build that cost $70,000 pays for itself in under two years, after which your only cost is minimal server hosting.

Key Features to Include in Your V1 Chat/Notification System

Don't try to build Slack on day one. A successful V1 focuses on a small, reliable set of core features. Everything else is V2.

Checklist for a Chat MVP

• User Authentication: Securely identify which user is sending/receiving messages.
• 1-on-1 Conversations: The ability for two users to message each other directly.
• Message History: Load the last 20-50 messages when opening a chat.
• Realtime Message Delivery: New messages appear instantly without a refresh.
• Basic UI: A list of conversations and a chat view. Don't overthink it.
• (Optional but recommended) Presence Indicators: A green dot to show who is currently online.
• (Optional but recommended) Read Receipts: A small checkmark to show a message has been seen.

Checklist for a Notifications MVP

• In-App Notification Feed: A dropdown or page (the "bell icon") showing a list of recent notifications.
• Unread Indicator: A red dot or count on the bell icon.
• Mark as Read: The ability for users to clear the unread state.
• Backend Event Triggers: Your primary backend should trigger notifications for key events (e.g., new order, new follower, task assigned).
• Basic Push Notifications: For 1-2 critical events that warrant interrupting the user when the app is closed.

Anything else—group chat, @mentions, reactions, file uploads, granular notification settings, snooze functionality—belongs on the V2+ roadmap.

Common Pitfalls and How to Avoid Them

Building realtime features is a minefield of potential problems. Here are the most common ones we see.

• Not Planning for Scale: Your solution works great with 10 test users, but what happens with 10,000 concurrent connections? You need to architect for scale from the start, considering connection limits, database performance under load, and the possibility of load balancing across multiple WebSocket servers.

• Ignoring Security: A WebSocket is an open door to your server. You must have a robust authentication and authorization strategy. Can any user subscribe to any channel? Can a malicious user spoof messages from someone else? Every single connection and message must be verified.

• Poor Offline/Connection Handling: Mobile users are constantly moving between WiFi and cellular, or through tunnels with no service. A robust app must gracefully handle disconnects and reconnects, queuing messages sent while offline and syncing history seamlessly upon reconnection.

• Battery Drain on Mobile: A chatty, poorly optimized mobile client can destroy a user's battery life. This requires careful management of the connection lifecycle and leveraging platform-native push notifications whenever possible.

• Forgetting the User Experience: The technical implementation is only half the battle. A confusing notification system or a clunky chat UI will drive users away. Think about clear states (sending, sent, delivered, read), intuitive navigation, and providing users control over what they are notified about.

These are the hard-won lessons that separate a prototype from a production-ready system. When you partner with a studio like Envert, you're not just buying code; you're buying the experience to navigate these pitfalls from day one. We've seen what breaks and we know how to build it right the first time.

Ready to Build? Here’s How We Can Help

Deciding how to implement realtime features is a major architectural choice with long-term consequences for your product's performance, user experience, and budget. The "buy" option is perfect for speed and validation, while the "build" option offers ultimate control and better long-term economics for core features.

If a custom, high-performance, and scalable realtime chat or notification system is on your roadmap, let's talk. We're a US-based studio of senior engineers and product experts who specialize in designing and building complex features for web apps, mobile apps, and SaaS platforms.

Book a free, no-obligation scoping call with our team at Envert. We’ll help you analyze the trade-offs, map out the features, define the architecture, and provide a realistic budget and timeline to bring your app to life.