Building Real-Time Apps Over Postgres: Why Many Developers Struggle (and How to Do It Right)

Oct 10, 2025 • Vela Team • 9 min read • RealtimePostgresSupabaseCDCWebSocketsVela

Realtime Postgres is the backbone of many modern applications. From dashboards to AI agents, teams want live data flowing directly from Postgres with minimal lag. Yet building reliable realtime systems on PostgreSQL is harder than it looks. Triggers and NOTIFY handle small signals, but they fail under scale, ordering, and authorization demands. Vela makes realtime Postgres durable, ordered, and production-ready.

The Challenge of Realtime Postgres

PostgreSQL wasn't originally designed for event streaming. Developers often start with LISTEN/NOTIFY or periodic polling. These work in prototypes but collapse when traffic grows or delivery guarantees matter. Missed messages, duplicated events, and inconsistent ordering appear as applications scale.

Achieving true realtime means combining durability, replay, and precise access control. Each of these requirements adds operational complexity if you build from scratch. Teams end up adding Kafka or Redis just to get predictable fan-out and persistence — splitting the data layer and increasing maintenance costs.

Why Traditional Methods Fall Short

Polling is easy but inefficient. It increases load and can't meet sub-second latency goals. LISTEN/NOTIFY improves latency but drops messages on restart and lacks durability. Triggers embed business logic inside the database, mixing state with orchestration. Logical decoding or change data capture (CDC) brings durability, but adds complexity through replication slots, consumer offsets, and fan-out handling.

Each option solves part of the problem but introduces new ones — either by creating operational overhead or sacrificing reliability. None alone deliver a complete realtime Postgres experience.

What True Realtime Postgres Requires

A durable realtime system must provide ordered delivery, replay, and access control. It should support idempotent messages and allow clients to reconnect without losing events. Channel-level authorization and rate limiting are essential to prevent abuse and leakage. Most importantly, the realtime layer must integrate directly with Postgres transactions, not bolt on top.

Building this manually means combining an outbox pattern, CDC pipelines, and gateway services. It works, but it's expensive to maintain. That's where Vela steps in.

Vela's Approach to Realtime Postgres

Vela brings realtime Postgres into a single, unified platform. Every database change can stream to durable channels backed by storage-level versioning. Messages are ordered, replayable, and linked to Postgres roles for access control. Clients subscribe through secure WebSockets with low-latency fan-out, and Vela handles backpressure automatically.

Instead of relying on external brokers, Vela runs the realtime layer inside your VPC as part of its Bring Your Own Cloud (BYOC) model. You maintain compliance, keep data residency, and get sub-second event delivery without sending rows to third-party queues.

The system supports replay and catch-up queries through versioned storage. Developers can open a branch of the database at any point in time — like a Git commit — and inspect historical events alongside current data.

Realtime Postgres for AI Backends

AI applications thrive on live context. Agents and pipelines depend on streaming updates from operational databases. With Vela, AI systems can consume realtime Postgres data safely and predictably. Durable channels feed embeddings, model fine-tuning, and feature stores without loss or inconsistency.

This design bridges transactional and analytical workloads. You can run inference and analytics over the same Postgres Data Platform without ETL lag. Vela's realtime layer ensures that AI backends see consistent, fresh data while keeping the system fully transactional.

Simplified Operations and Observability

Vela integrates observability into every channel. Teams can inspect message latency, subscriber counts, and throughput directly from the control plane. Metrics expose slow consumers and replay rates, making performance predictable. With built-in dead-letter queues, failed deliveries never vanish — they can be retried or inspected later.

Because everything runs in your VPC, standard tools for metrics, tracing, and alerts still apply. Vela fits seamlessly into your existing monitoring pipelines.

The Result: Realtime Postgres That Scales

Vela turns PostgreSQL into a true realtime data platform. It merges the reliability of a database with the immediacy of an event stream. You get durable delivery, replay, authorization, and observability — all without managing external brokers or losing compliance.

Frequently Asked Questions

What is realtime Postgres?

Realtime Postgres enables your application to receive live updates directly from your database as data changes occur. Instead of polling or using external brokers, changes flow through durable channels with minimal latency. This is essential for features like live dashboards, collaborative editors, and AI agent backends that need fresh context.

Why should I use realtime Postgres instead of a message queue?

Message queues add operational complexity and split your data layer. With realtime Postgres, your source of truth remains in Postgres—no need to sync data to Kafka or Redis. Vela's approach delivers durability, replay, and authorization built directly into the database, reducing moving parts and maintenance overhead.

Does LISTEN/NOTIFY provide realtime capabilities?

LISTEN/NOTIFY works for simple use cases but has critical limitations. It drops messages on client disconnect, has no durability, lacks replay, and provides no ordering guarantees at scale. For production systems requiring reliable event delivery, ordered processing, and the ability to catch up on missed events, Vela's durable channels are a better choice.

How does Vela handle authorization for realtime events?

Vela integrates realtime channels with Postgres roles (RBAC). Events published through durable channels respect your existing row-level security policies. Subscribers only receive events for rows they have permission to access, ensuring data remains secure without duplicating authorization logic.

Can I replay missed events with Vela's realtime system?

Yes. Vela's durable channels maintain a complete history of events backed by storage-level versioning. If a subscriber disconnects or falls behind, it can replay missed events from any point in time. This is critical for catching up after network failures or when adding new consumers to existing channels.