PUSH Technologies - An Overview

PUSH technologies allow servers to deliver updates to clients the moment something meaningful happens. Unlike traditional request/response patterns, PUSH reverses the flow: the server becomes the initiator.

This article provides a clear architectural overview of the major PUSH mechanisms, how they behave, where they fit, and how to choose between them. Deep‑dive technical articles for each protocol are linked throughout.

Why PUSH Matters

Modern systems increasingly expect events to arrive instantly. Users no longer tolerate:

• polling delays
• stale dashboards
• race conditions between systems
• manual refresh cycles

PUSH solves these challenges by establishing:

• a persistent or semi‑persistent communication channel
• a subscription or routing mechanism
• an event‑triggered delivery engine

PUSH enables:

• real‑time dashboards
• collaborative experiences
• workflow updates
• IoT telemetry
• notification ecosystems
• cross‑system synchronisation

The Major PUSH Technologies

This overview covers the six primary PUSH families used across web, mobile, and IoT systems:

• Server‑Sent Events (SSE) — one‑way server → client streaming
• WebSockets — full‑duplex, bidirectional communication
• MQTT v5 — IoT‑focused publish/subscribe messaging
• Long‑Polling — legacy, simulated PUSH using held HTTP requests
• Web Push API — browser notifications delivered via Service Workers
• Web Push Protocol (RFC 8030) — server → push service → browser channel

Each solves a different architectural problem. None replaces the others.

Summary Comparison Table

Technology	Directionality	Ideal Use Cases	Complexity
SSE	Server → Client	Notifications, dashboards, workflow events	Low
WebSockets	Full‑duplex	Chat, collaboration, presence, shared editing	Medium–High
MQTT v5	Publish/Subscribe	IoT, telemetry, distributed systems	Medium
Long‑Polling	Simulated PUSH	Legacy fallback, older browsers/servers	Low
Web Push API	Server → Browser (via SW)	Notifications when app is closed	Medium
Web Push Protocol (RFC 8030)	Server → Push Service → Browser	Reliable background delivery	Medium

The Universal PUSH Lifecycle

Regardless of the technology, PUSH systems follow a similar sequence:

1. Intent / Discovery

  The client declares interest (“I want updates for X.”)

1. Channel Establishment

  A connection or subscription pipeline is created.

1. Subscription Registration

  The server/broker maps the client to topics, routes, or events.

1. Delivery

  Events are pushed without polling.

Technologies differ only in how they perform these steps.

When to Use Which Technology

• Use SSE when you need simple, reliable one‑way streaming over HTTP.
• Use WebSockets when both sides must send events at any time.
• Use MQTT when you need scalable pub/sub or IoT‑style routing.
• Use Long‑Polling for maximum compatibility with legacy environments.
• Use the Web Push API for system‑level browser notifications.
• Use the Web Push Protocol when communicating with push services.

High‑Level Architectural Considerations

Scalability

• SSE and WebSockets require persistent connections at scale.
• MQTT brokers handle very large fan‑out and dynamic topic routing.
• Web Push offloads scaling to the browser vendor’s push service.

Security

• All modern PUSH channels require TLS.
• Web Push enforces encrypted payloads even after leaving your server.
• MQTT requires careful ACL and topic‑level access design.

Backwards Compatibility

• Long‑Polling remains the universal fallback.
• SSE degrades to long‑polling in some environments.
• WebSockets require explicit upgrade support.

Operational Lifecycle

• WebSockets require heartbeat handling.
• MQTT requires broker management and topic governance.
• Web Push requires subscription renewal logic.

Linked Deep‑Dive Articles

For full technical detail, see the following dedicated articles:

• PUSH: Server‑Sent Events (SSE)
• PUSH: WebSockets
• PUSH: MQTT v5
• PUSH: Long‑Polling
• PUSH: Web Push API
• PUSH: Web Push Protocol (RFC 8030)

Each sub‑article includes:

• protocol flows
• wire‑level behaviour
• lifecycle diagrams
• example frames/messages
• deployment considerations
• common pitfalls and diagnostics

Related Topics

• Real‑Time Systems
• Event‑Driven Architecture
• Polling vs PUSH Models
• Distributed Messaging Patterns