Your users expect data to appear the moment it changes. A new trade listing, a loot box animation, a notification badge, if there is a visible delay, the experience feels broken. Real time architecture is no longer a nice to have. It is table stakes for any application where users interact with live data.
But most teams pick the wrong approach. They reach for WebSockets when polling would suffice, or they use polling when they need persistent connections. Choosing the wrong real time pattern is one of the most common software architecture mistakes we see in production systems.
There are three primary approaches to real time data delivery. Here is how they compare, with real production examples from systems we have built.
Polling: The Simplest Option
Polling is the most common approach. The client asks the server for updates on a fixed interval, every 5 seconds, every 30 seconds, every minute.
When polling is the right call:
- Dashboards that refresh every 30-60 seconds. The simplicity outweighs the latency cost.
- Background sync for non critical data. User preferences, configuration, app version checks.
- Low traffic internal tools. If you have 50 users, polling every 10 seconds generates trivial load.
When polling breaks down: 10,000 concurrent users polling every 5 seconds means 2,000 requests per second, most returning "nothing changed." You are paying for compute and database queries to deliver empty responses. For chat or live trading, a 5-second delay is unacceptable.
Server Sent Events: The Underrated Middle Ground
SSE is the most underused real time technology in production. It is simpler than WebSockets, more efficient than polling, and solves 60% of real time use cases with a fraction of the complexity.
How it works: The client opens a single HTTP connection. The server holds it open and pushes data whenever something changes. It is one way: server to client only.
When SSE is the right call:
- Notifications and alerts. Server pushes "you have a new message", client just listens.
- Live feeds and activity streams. Timelines, news tickers, price updates.
- Progress indicators. File uploads, long running jobs, deployment pipelines.
Why it is underrated: SSE works over standard HTTP. It passes through proxies and load balancers without special configuration. It auto reconnects on drop. The browser API is five lines of JavaScript.
Limitations: One way only. Browsers limit concurrent SSE connections per domain to around six.
WebSockets: Full Duplex Power
WebSockets are the heavyweight option. A persistent, full duplex connection where both sides can send messages at any time.
When WebSockets are the right call:
- Chat and messaging. Both directions are equally active.
- Collaborative editing. Every keystroke propagates to every participant.
- Gaming. Player inputs flow to the server; game state flows back.
- Live animations. When we built GameLootBoxes, WebSockets drove the real time loot box animation system. The server determines the outcome using a provably fair algorithm and streams the reveal sequence back, the dramatic pause, the item reveal, the rarity effect, all coordinated at sub 100ms latency. Polling would have felt like watching a slideshow.
The complexity cost: WebSockets require sticky sessions or a pub/sub layer (Redis, NATS) for multi server setups. They do not play well with some corporate proxies. Connection management, disconnects, reconnects, auth refresh, adds real engineering work.
Do not reach for WebSockets because they sound impressive. Reach for them when you genuinely need bidirectional, low latency communication.
Supabase Real Time: The Cheat Code
There is a fourth option: managed real time built on your database. Supabase Realtime wraps PostgreSQL's `LISTEN/NOTIFY` in a client SDK that gives you live data subscriptions with zero WebSocket infrastructure to manage.
This is exactly what powers the real time inventory system in Traderly. When a seller lists a new item, every buyer browsing that category sees it appear instantly. When someone purchases an item, it disappears from every other user's screen. The entire flow from listing to purchase to inventory update happens in under 200ms, and Supabase Realtime broadcasts every state change without a single line of WebSocket server code.
We covered Supabase in our modern startup tech stack, but its real time capability deserves special attention here.
When it is enough: Your real time data originates from database mutations. Live dashboards, inventory systems, notification feeds, collaborative lists, order tracking.
When you need raw WebSockets: Your real time data does not originate from database changes. GameLootBoxes needed WebSockets because the animation state machine runs in memory, frames and timing data are computed and streamed in real time, not stored in database rows.
Choosing the Right Approach
Use polling when: freshness tolerance is 10+ seconds, traffic is low, and you want zero additional infrastructure.
Use SSE when: data flows server to client only, you need sub second delivery, and you want to stay on standard HTTP.
Use WebSockets when: you need bidirectional communication with sub 100ms latency.
Use Supabase Realtime when: your real time data is driven by database changes and you want live updates without managing infrastructure.
Most production systems use more than one approach. Traderly uses Supabase Realtime for inventory updates and standard HTTP for trade execution. GameLootBoxes uses WebSockets for animations and polling for leaderboard refreshes. Pick the simplest approach that meets each feature's requirements.
Build Real Time That Scales
If you are building something that needs to feel instant, whether that is a trading platform, a gaming experience, or a collaborative tool, the architecture decisions you make now determine your latency, infrastructure costs, and engineering overhead for years. We have built real time systems serving 100K+ concurrent users and delivering sub 100ms animations.