Building Realtime Features: A Founder's Playbook for Chat & Notifications

Your users expect a dynamic, living app. Dead UIs are a death sentence. Whether it's a notification popping up the second an action happens, a cursor moving in a collaborative document, or a message appearing instantly in a chat window, realtime features are no longer a nice-to-have. They are table stakes for engagement and retention.

Founders and product leaders get this. The question isn't if you need these features, but how you'll build them. You’re facing a classic, high-stakes decision: build it from scratch or buy a ready-made solution?

Get this wrong, and you could burn six figures and months of runway on a buggy, unscalable system. Or you could get locked into a third-party service that bleeds you dry as you grow.

This is the playbook for getting it right. We'll cut through the noise and give you the data, checklists, and cost breakdowns to make a confident decision for your web app, mobile app, or SaaS MVP.

What *Is* a Realtime System? The Core Concepts

Before we talk strategy, let's demystify the tech. At its heart, a realtime system is about one thing: pushing data from your server to the client (the user's browser or phone) instantly, without the user having to refresh the page.

Traditionally, the web works on a request-response model. Your browser asks for a web page, the server sends it. To get new information, you have to ask again. This is inefficient for live updates. Here’s how modern apps solve this, from worst to best:

• Short Polling: The client asks the server for updates every few seconds. Think of a kid in a car asking "Are we there yet?" every 30 seconds. It's noisy, inefficient, and generates a lot of useless network traffic. It's almost never the right choice for a true realtime experience.

• Long Polling: A smarter version. The client asks the server for an update, but the server holds the connection open until it actually has something new to send. Once it sends the update, the client immediately opens a new connection. This is far better than short polling, but it can be complex to manage server connections at scale.

• Server-Sent Events (SSE): A one-way street. The server can push data to the client whenever it wants, but the client can't send data back over the same connection. This is perfect for things like stock tickers, live activity feeds, or system-wide notifications where the user is just a consumer of information.

• WebSockets: The gold standard. This establishes a persistent, two-way connection between the client and the server. Data can flow freely in either direction at any time. This is the technology that powers modern chat apps, collaborative tools (like Figma), and multiplayer games. It’s powerful but also the most complex to manage, scale, and secure yourself.

Understanding these options is key, because your choice of technology is directly tied to the build vs. buy decision.

The "Build It Yourself" Path: Architecture & Tech Stack

Deciding to build your own realtime infrastructure is a major engineering commitment. It’s not just about writing the code for a chatbox. You are signing up to build, manage, and scale a complex distributed system. If this feature is the absolute core of your product—if you're building the next Slack or Discord—this might be the only path.

Backend Architecture

A custom realtime backend needs a few key components:

1. A WebSocket Server: This is the heart of the system. It manages all active connections from users. Popular choices include Node.js with libraries like Socket.IO or ws, or frameworks in other languages like Elixir with Phoenix (renowned for its ability to handle millions of connections) or Go (for its performance and concurrency).
2. A Message Broker/Publisher: When User A sends a message to User B, the server needs to know which connection belongs to User B. At scale, you'll have multiple WebSocket servers. A message broker like Redis Pub/Sub or RabbitMQ is used to broadcast messages across all your servers to find the right recipient.
3. A Database: You need to persist the messages. A standard PostgreSQL database is often sufficient for storing chat history. You'll need to design your schemas carefully for efficient querying (e.g., indexing by conversation_id and timestamp).
4. Presence Management: How do you show who is "online"? This is surprisingly hard. You need a fast, ephemeral data store like Redis to track connection states in realtime. Updating a traditional database for every connect/disconnect event is a recipe for disaster.

Frontend Implementation

On the client-side, you'll use a corresponding library (e.g., socket.io-client) to establish the WebSocket connection. Your frontend code will be responsible for:

• Listening for incoming events (new_message, user_online, user_started_typing).
• Updating the UI in response to those events.
• Managing the application state (e.g., using React Query or Redux to store messages).
• Handling connection errors and reconnections gracefully.

The Hidden Costs of Building: The Iceberg Under the Surface

This is where founders get into trouble. The cost isn't just developer salaries for the initial build. The real cost is the long-tail of complexity.

• DevOps & Scalability: Scaling WebSocket servers is not like scaling stateless web servers. You need specialized load balancing (sticky sessions), horizontal scaling strategies, and a robust deployment pipeline. A single server might handle a few thousand concurrent connections, but what happens when you hit 50,000? This is a hard problem that requires senior DevOps expertise.
• Security: How do you authenticate WebSocket connections? How do you ensure a user can only subscribe to their own notification channels? You need to handle token-based authentication, channel-level authorization, and protect against denial-of-service attacks.
• Reliability & Redundancy: What happens if a server crashes? Do users get disconnected? Do messages get lost? You need to build a system with failovers, message delivery guarantees (e.g., "at-least-once" delivery), and reconnection logic.
• Maintenance: Your chosen stack will have updates, security patches, and deprecated libraries. This isn't a "set it and forget it" system. It requires ongoing engineering attention, forever.

Ballpark Cost: A conservative estimate to build a production-ready, scalable chat system from scratch is $80,000 - $200,000+ in initial engineering costs. This typically involves 2-3 engineers working for 3-6 months. This complexity is why many founders partner with an expert studio. At Envert, we've architected and built dozens of these complex systems. We can navigate the pitfalls of scalability and security, saving our clients months of expensive trial-and-error and ensuring their core features are built on a rock-solid foundation.

The "Buy" Path: Leveraging Third-Party Services (PaaS)

The alternative is to outsource the entire realtime infrastructure to a Platform-as-a-Service (PaaS) provider. You integrate their SDK into your app, and they handle the complexity of connections, scaling, and reliability. This is the fastest way to get to market.

Top Players in the Game

The market is mature, with several excellent providers. They generally fall into two categories: pure infrastructure and full-featured chat solutions.

• Pusher (by Ably) & Ably: These are infrastructure plays. They give you the WebSocket primitives (channels, events, presence) and you build your UI and business logic on top. They are incredibly powerful, scalable, and reliable. Ably, in particular, has strong guarantees around message ordering and delivery.
• Sendbird & Stream: These are more full-featured "Chat-as-a-Service" platforms. They provide the infrastructure plus pre-built UI components, moderation tools, typing indicators, read receipts, and more. They are the fastest way to launch a full-blown chat experience that rivals major apps.

A Concrete Pricing Breakdown

Pricing for these services can feel opaque, but let's make it concrete. Imagine you're building a SaaS tool and expect to have 10,000 Monthly Active Users (MAU). Your app sends basic notifications (e.g., "Task Assigned").

Service	Model	Estimated Monthly Cost (for 10k MAU)
Ably	Connections & Messages	~$99 (Pay-as-you-go, covers up to 6M messages and 60k peak connections)
Sendbird	Monthly Active Users (MAU)	$399 (Pro plan, covers up to 5k MAU) -> you'd need the next tier, likely $600+
Stream	Varies (MAU, Calls, etc.)	Starts at $499/mo for their Chat Startup plan.

As you can see, the pricing models and costs vary dramatically. For simple notifications, a service like Ably is incredibly cost-effective. For full-featured chat, Sendbird and Stream are more expensive but save you enormous development time.

The Trade-offs of PaaS

While speed is a huge advantage, it's not a free lunch.

• Cost at Scale: The monthly fees can become substantial as you grow. A wildly successful app could end up paying tens of thousands per month to a chat provider. Run the numbers for your 12-month and 24-month growth projections.
• Vendor Lock-in: Migrating from one provider to another (or to a self-built solution) is painful. You're building your app around their specific API and data structure.
• Less Control: Need a highly custom feature that the provider doesn't support? You're out of luck. You are limited to their feature set and roadmap.
• Data Sovereignty: Your user data and conversations are stored on someone else's servers. For apps in sensitive domains like healthcare (HIPAA) or finance, this can be a non-starter.

Decision Checklist: Build vs. Buy for Your MVP

There is no single right answer. It depends entirely on your business context. Use this checklist to guide your thinking.

You should strongly consider BUILDING if:

• The realtime feature is your core product and primary differentiator (e.g., you are building a new collaborative design tool).
• You require 100% control over the user experience and feature roadmap.
• You have strict data residency or compliance requirements (e.g., HIPAA).
• You have a strong, senior in-house engineering team with proven experience in distributed systems and DevOps.
• You have the capital and time to invest in a long-term strategic asset.

You should strongly consider BUYING if:

• Speed to market is your absolute top priority.
• The realtime feature is ancillary to your core value proposition (e.g., notifications in a project management app).
• You want to validate the need for the feature before investing heavily in it.
• Your engineering team is small or focused on other core business logic.
• You have a predictable user growth model and the PaaS costs are acceptable within your financial plan.

Real-World Scenarios & Timelines

Let's apply this framework to two common scenarios.

Scenario 1: A B2B SaaS MVP with Notifications

You're building a new project management tool. You need to notify users when they are assigned a task or mentioned in a comment.

• Recommendation: Buy. This is a classic ancillary feature. Your value prop is project management, not notification delivery.
• Choice: Ably or Pusher.
• Timeline: A single engineer can integrate this in 1-2 weeks.
• Cost: Starts around $50-$100/month and scales predictably. The opportunity cost of building this yourself is massive.

Scenario 2: A Consumer Mobile App with Group Chat

You're building a social app for a niche community, and rich group chat is the central feature.

• Recommendation: This is tougher. For an MVP, you could Buy using Sendbird or Stream to get to market in months, not years. However, if the chat experience itself needs to be highly unique and you project massive growth, you must have a long-term plan to Build.
• Hybrid Approach: Start with a PaaS provider for your MVP to validate the idea. If you get traction, raise a round and invest in building your own proprietary solution to control costs and the user experience. Migrating will be a challenge, but it's a planned challenge.
• Timeline (Buy): 1-2 months to integrate a full-featured chat using Stream/Sendbird.
• Timeline (Build): 4-9 months for a robust, scalable, custom solution. At Envert, we specialize in these end-to-end custom builds for both web and mobile. We help founders architect a system that's not just functional for the MVP, but ready to handle millions of users, providing a core asset that becomes part of the company's IP.

It's Your Call, But Don't Make It Alone

The decision to build or buy your realtime system is one of the most critical architectural choices you'll make. It has a direct impact on your runway, your go-to-market speed, and your ability to scale.

Building gives you control and a long-term asset but comes with high upfront costs and technical risk. Buying gets you to market fast but introduces vendor lock-in and potentially punishing costs at scale.

Analyze your core business, your team's capabilities, and your financial runway. Use the checklist. Run the numbers. There is a right answer for your business.

Feeling stuck? This is complex stuff, and a bad decision here can cost you dearly. If you're building a new web app, mobile app, or SaaS platform and are weighing these trade-offs, let's talk. Book a free, no-obligation scoping call with our senior partners at Envert. We’ll help you analyze your specific situation and architect a solution that balances speed, cost, and long-term scalability. We build these systems every day; let our experience be your advantage.