What is a Real-Time App and Why Does it Matter?

Transport and delivery real time app

Real-time apps technical details

Architecture Patterns for Real-Time Systems

Real-time systems require architectural patterns to handle high-throughput, low-latency data flows with resilience and scalability. Pub/Sub is foundational, enabling decoupled communication where publishers emit events and subscribers react asynchronously. Event-driven architecture builds on this, treating events as first-class citizens to trigger workflows and microservices dynamically. Microservices enhance agility and fault isolation, allowing independently deployable units to scale horizontally. Serverless patterns, particularly with FaaS (Functions as a Service), further decouple infrastructure concerns by dynamically scaling compute in response to real-time triggers. These patterns enable production-grade systems capable of reacting to high-velocity data while maintaining operational flexibility and high availability.

Choosing the Right Transport Protocol: WebSockets vs SSE vs HTTP/2:

Transport protocol selection directly impacts the performance, reliability, and scalability of real-time applications. WebSockets offer full-duplex, low-latency communication. Server-Sent Events (SSE) provide a simpler, unidirectional stream from server to client, making them efficient for use cases like live feeds or monitoring dashboards. HTTP/2 enables multiplexed streams over a single connection and is better suited for structured API communication with improved performance over traditional HTTP/1.1. In production, fallback strategies—such as falling back from WebSockets to long polling—are critical for handling network constraints or proxies. Benchmarking these protocols under load, latency, connection management and reconnection scenarios ensures optimal selection of your system’s real-time guarantees and user experience goals.

State Management and Synchronization

State management and synchronization are key challenges in distributed real-time apps, balancing consistency and performance across global systems. Conflict-free Replicated Data Types (CRDTs) enable state convergence without central coordination, ensuring strong eventual consistency for collaborative apps. Operational Transformation (OT) supports real-time collaboration by transforming operations to maintain shared state consistency. Cache invalidation keeps data up to date with minimal latency, while consistency models like eventual consistency prioritize performance over temporary inconsistencies, favoring availability and partition tolerance. Strong consistency models ensure a single truth but may increase latency and reduce fault tolerance. The choice of approach depends on the app's needs—whether it requires immediate consistency (e.g., financial transactions) or can tolerate temporary inconsistencies (e.g., social media feeds).

Real-time Message Brokers and Event Buses: Kafka, NATS, Redis Streams, MQTT, or PubNub?

• Apache Kafka is the de facto standard for high-throughput, durable event streaming. Its distributed log architecture supports strong ordering and persistence guarantees, making it ideal for event sourcing, audit trails, and real-time analytics pipelines at scale. However, it comes with operational complexity and higher latency.
• NATS targets ultra-low-latency, high-performance messaging with minimal overhead, optimized for microservice architectures and internal control planes. While it lacks built-in durability by default, it can be extended with JetStream for persistence and stream replay. Ideal for scenarios where speed and simplicity are paramount, and message loss can be tolerated or mitigated.
• Redis Streams offers a hybrid approach—fast, in-memory processing with stream semantics and optional persistence. It’s well-suited for high-speed data ingestion, lightweight task queues, and real-time monitoring where low latency is critical and full durability is not a strict requirement.
• MQTT is tailored for IoT use cases, providing a lightweight publish/subscribe protocol optimized for constrained devices and unreliable networks. It supports various QoS levels but is typically brokered through a dedicated MQTT server like Mosquitto or EMQX.
• PubNub is a fully managed, globally distributed real-time messaging platform designed for application-layer, with built-in pub/sub, presence, message history, access control, and edge delivery—eliminating the need to manage infrastructure. While it’s not a replacement for low-level brokers like NATS or Kafka, it excels in delivering end-user experiences at a global scale.

Ultimately, broker selection should be driven by message volume, delivery guarantees, network topology, operational overhead, and whether the messaging layer is infrastructure-facing or user-facing. In many production systems, a hybrid approach—using Kafka for durable backend pipelines, NATS for service-to-service traffic, and PubNub for real-time user updates—is often the most scalable and maintainable solution.

PubNub powers real-time apps.

But how do real-time apps work? Mobile devices exchange small packets of data in under 1/10 of a second—but that speed doesn’t happen automatically. Developers need a real-time infrastructure to make it work. That’s where PubNub comes in.

Building and maintaining this kind of system yourself is complex, expensive, and time-consuming. PubNub simplifies it by offering a globally scaled, reliable real-time network—so developers can focus on building their apps, not the infrastructure behind them.

From chat and live updates to IoT and gaming, PubNub provides the backbone for real-time experiences across industries. It’s known as IaaS, data streaming, or simply: a real-time network. That’s what we do.

How can PubNub help you?

PubNub assists developers in building, delivering, and managing real-time interactivity for web apps, mobile apps, and IoT devices—all while maintaining user retention. Our platform is built on the industry's largest and most scalable real-time edge messaging network. As of 2024, PubNub supports a vast variety of the latest technologies and protocols, ensuring that your applications stay ahead in the rapidly progressing tech world.

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