Choosing Between Polling, SSE, and WebSockets in Production

How to think about real-time communication, not just how to implement it

Introduction

This article is not a tutorial on how to implement polling, Server-Sent Events (SSE), or WebSockets.
It assumes you already understand the basics.

Instead, it focuses on how to decide between them in production systems, where infrastructure constraints, reliability, and long-running clients matter more than protocol diagrams.

The question is rarely “Which technology is better?”
The real question is “Which communication model fits this system?”

The goal is not to recommend a single solution, but to show how the same problem can lead to different choices depending on constraints.

I’ll walk through that decision-making process using a real, production-tested system as context, without turning this into a framework-specific guide.

The Communication Problem, Stripped Down

The system in question is a LAN-first, event-based photo sales platform, used during long-running live events.
If you want the broader context, here’s a short project overview: Field-Ready Event Photo Sales System.

Tablets browsing a photo gallery
Admin panels managing orders
A dedicated screen showing or clearing QR codes

Several parts of the UI need to react to server-side changes:

New photos appearing in the gallery
New orders becoming visible to admins
Order state changes reflected immediately
Screens updating without manual refresh

All state-changing actions already happen through regular HTTP requests.
Clients create orders, confirm payments, or trigger actions via REST.

What was missing was a way to notify other connected clients that something had changed, without aggressive polling or page reloads.

That’s where the choice between polling, SSE, and WebSockets becomes relevant.

Polling: The Baseline Often Dismissed Too Quickly

Polling is often dismissed as “outdated,” but it’s still the baseline against which everything else should be evaluated.

It has clear advantages:

Works everywhere
Stateless and easy to reason about
Trivial to implement and debug

It also has clear trade-offs:

Unnecessary requests when nothing changes
Delayed updates between polling intervals
Wasted resources with many long-running clients

In this system, polling was acceptable for low-priority data, but it was a poor fit for gallery refreshes and admin updates. The cost of repeatedly asking “has anything changed?” outweighed its simplicity.

Polling wasn’t wrong - it just wasn’t the right tool for the core real-time paths.

Understanding What “Bidirectional” Actually Means

A common source of confusion is the idea of bidirectional communication.

At first glance, many systems appear bidirectional even when they’re not. A client sends data to the server, the server processes it, and other clients receive updates.

That flow can be implemented with:

HTTP requests for writes
SSE for notifications

This works well, but it relies on two different communication mechanisms.

With WebSockets, sending and receiving happens over the same persistent connection.
With SSE, receiving is persistent, while sending still uses regular HTTP requests.

The difference is not about capability, but about how the connection behaves:

One shared channel vs. separate mechanisms
Connection state vs. stateless requests
Added complexity vs. simplicity

Understanding this distinction is often the turning point in choosing the right approach.

Server-Sent Events as a Notification Layer

Server-Sent Events follow a simple model:

The client opens an HTTP connection
The server keeps it open
Events are pushed whenever something relevant happens

Communication flows only from server to client.

This works especially well when:

The server is the source of truth
Clients already use REST to change state
Real-time updates are notifications, not conversations

In practice, SSE becomes a notification layer on top of a REST-based system:

A client sends a POST request to create or update data
The server processes and persists the change
The server emits a lightweight event
Connected clients react and fetch fresh data if needed

Business logic stays in REST.
SSE is used purely for synchronization signals.

This separation turned out to be both robust and easy to maintain.

Automatic Reconnects and Long-Running Clients

One aspect of SSE that matters in real systems is automatic reconnection.

Even in stable LAN environments with controlled hardware, browser clients are not guaranteed to maintain a perfect connection forever. Tabs can be suspended, processes restarted, or network interfaces briefly reset.

With SSE, the browser automatically attempts to reconnect when the connection drops. When the client becomes active again, the event stream resumes without user intervention.

For long-running, unattended clients - gallery tablets or kiosk-style screens - this behavior significantly reduces operational friction. The system recovers quietly instead of requiring manual refreshes or user actions.

Why WebSockets Were Not the Right First Choice

WebSockets would have worked technically. That was never the question.

They shine in scenarios where:

Clients push frequent real-time messages
Latency in both directions is critical
Interactions are conversational or continuous

They also introduce additional concerns:

Connection lifecycle management
Reconnection strategies
Stateful connections at scale

In this context, none of the core features required real-time client-to-server messaging. All writes already flowed through HTTP endpoints, and that model was reliable.

Adding WebSockets would have meant:

Implementing reconnection logic manually
Managing connection state during long-running events
Debugging stateful connections when issues arise
No measurable improvement in user experience

The return on investment didn’t justify the added complexity.

A Practical Decision Framework

When choosing between polling, SSE, and WebSockets, these questions tend to matter more than protocol details:

Who initiates updates?
- Mostly server → client → SSE
- Frequent client → server → WebSockets
How often do updates happen?
- Seconds or less → SSE or WebSockets
- Tens of seconds → polling is often enough
How long do clients stay connected?
- Minutes → any approach
- Hours → SSE handles this gracefully
- Days → reconsider persistent connections entirely
What is the operational environment?
- Simple HTTP stack → SSE or polling
- Complex interactive flows → WebSockets

It’s also worth considering what an “idle” connection costs in your environment.
In cloud or serverless setups, a large number of long-lived connections can increase CPU, memory, or process-level costs, even when very little data is being transmitted.
In controlled environments with a known number of clients, that trade-off looks very different and is often predictable.

These questions don’t produce a single correct answer, but they help eliminate the wrong ones early.

Quick Matrix

Criteria	Polling	SSE	WebSockets
Direction	Client → Server	Server → Client	Bidirectional
Complexity	Low	Low–Medium	High
Latency	Interval-based	Near real-time	Near real-time
Scalability	Poor	Good with HTTP/2	Good with infra support
Best Fit	Legacy, fallback	Dashboards, notifications	Interactive apps

Common Decision Anti-Patterns

Anti-pattern 1: “WebSocket because it’s modern”
Choosing technology based on hype rather than requirements.
Reality: SSE is often simpler and sufficient for server-driven updates.

Anti-pattern 2: “Polling is always bad”
Dismissing polling without considering its trade-offs.
Reality: Stateless, simple, debuggable - often good enough for non-critical paths.

Anti-pattern 3: “Pick one and use everywhere”
Forcing a uniform communication model across all features.
Reality: Hybrid approaches are often the best solution.

Anti-pattern 4: “Real-time means sub-second latency”
Assuming all updates must be instantaneous.
Reality: Many “real-time” features work perfectly well with small, acceptable delays.

Looking Ahead

The platform is planned to expand with an online storefront, introducing new interaction patterns. Some of those may justify WebSockets, especially for interactive or collaborative features.

That evolution doesn’t invalidate the current choice.
It reinforces the idea that communication models should evolve with requirements, not be locked in prematurely.

Final Thoughts

Polling, Server-Sent Events, and WebSockets are not competing technologies. They solve different problems.

Polling favors simplicity and resilience
SSE favors server-driven updates with minimal overhead and automatic reconnection
WebSockets favor true bidirectional interaction

The most important skill is not knowing how to implement each one, but knowing when to use them - and when not to.

In this system, SSE provided the right balance of simplicity, reliability, and real-time behavior. In another system, the answer may be different - and that’s exactly the point.