/neon-realtime

FIRST: Use the parent neon skill for a Neon overview, getting started with Neon, Neon development best practices, and more.

If the neon skill is not installed, fetch it from https://neon.com/docs/ai/skills/neon/SKILL.md or install it with:

neon skills -s neon -y

Neon Realtime

Neon's Realtime makes any SQL query live. Subscribe in realtime to your Lakebase Postgres database. Develop apps and agents with end-to-end reactivity using type-safe live queries and optimistic mutations.

Realtime is new and in beta, so its APIs aren't in your training data. Start from the core pattern below, and read each section's reference file before writing that code.

How It Works

Realtime's layers compose: a live query engine inside Postgres, the Live SQL API (a WebSocket API), lower-level client SDKs (seal(), subscribe()), and reactivity primitives such as useLiveQuery.

1. In trusted backend code, define a live query (any read-only SQL, including joins, aggregates, ordering and limits), seal it with NEON_REALTIME_SECRET and expose it from an authenticated endpoint or server function. The client can't read or change a sealed query's SQL or parameters.
2. The client subscribes with the sealed query. It receives the full initial result, then each committed transaction's changes as one batch. Results stay consistent, but delivery of every change event isn't guaranteed.
3. Writes go through your own API, which returns each write's txid for awaitTxId().

Core Pattern

The guides' chat app, with messages authorized through channel_members. The backend seals the query and returns each write's txid:

import { createRealtime, rawSql } from "@neon/realtime/server"
import { drizzleAdapter } from "@neon/realtime-drizzle"
import { and, desc, eq, getTableColumns, sql } from "drizzle-orm"
import { Hono } from "hono"
import { HTTPException } from "hono/http-exception"
import { requireUser } from "./auth"
import { db } from "./db"
import { channelMembers, messages, type Message } from "./schema"

export const realtime = createRealtime({ secret: process.env.NEON_REALTIME_SECRET!, db: "neondb", adapter: drizzleAdapter() })

// Each selected key must match its column name
export function messagesQuery(userId: string, channelId: number) {
  return db
    .select(getTableColumns(messages)).from(messages)
    .innerJoin(channelMembers, eq(channelMembers.channel_id, messages.channel_id))
    .where(and(eq(channelMembers.user_id, userId), eq(messages.channel_id, channelId)))
    .orderBy(desc(messages.created_at))
    .limit(50)
}

// Or raw SQL
const rawMessagesQuery = (userId: string, channelId: number) => rawSql<Message>(
    `SELECT messages.author_id, messages.body, messages.channel_id, messages.created_at, messages.id FROM messages
     INNER JOIN channel_members ON channel_members.channel_id = messages.channel_id WHERE channel_members.user_id = $1 AND messages.channel_id = $2 ORDER BY messages.created_at DESC LIMIT 50`,
    [userId, channelId]
  )

// The id of the transaction that made the change, read in the write's own RETURNING
const txid = sql<string>`pg_current_xact_id()::text`

const app = new Hono()
  .post("/api/v1/messages/live", async (c) => {
    const user = await requireUser(c)
    const { channelId } = await c.req.json<{ channelId: number }>() // validate input
    return c.json(await realtime.seal({ query: messagesQuery(user.id, channelId) }))
  })
  .post("/api/v1/messages", async (c) => {
    const user = await requireUser(c)
    const { id, channelId, body } = await c.req.json<{ id: string; channelId: number; body: string }>() // validate input
    // One statement. The membership row supplies channel_id and author_id, so only a member's message is inserted.
    // List every column in table order, alias each sql field, and cast untyped params (they resolve to text)
    const [sent] = await db.insert(messages).select(
      db.select({
          id: sql`${id}::uuid`.as("id"), channel_id: channelMembers.channel_id, author_id: channelMembers.user_id,
          body: sql`${body}`.as("body"), created_at: sql`now()`.as("created_at"),
        })
        .from(channelMembers)
        .where(and(eq(channelMembers.channel_id, channelId), eq(channelMembers.user_id, user.id)))
    ).returning({ txid })
    if (!sent) throw new HTTPException(403, { message: "Not a member of this channel" })
    return c.json({ kind: "committed", txid: sent.txid })
  })

The React frontend subscribes and sends optimistic messages:

import { createRealtimeClient, type SealedLiveQuery } from "@neon/realtime/client"
import { drizzleParsers } from "@neon/realtime-drizzle/client"
import { useLiveQuery } from "@neon/realtime-react"
import { startTransition, useCallback, useOptimistic } from "react"
import type { Message } from "../backend/schema"
import { fetchSealedMessages, sendMessage } from "./api"

// One client per app, because subscriptions share its connection. Wrap the app in <RealtimeProvider client={client}>
export const client = createRealtimeClient({ url: import.meta.env.VITE_NEON_REALTIME_URL, parsers: { ...drizzleParsers } })

const NO_MESSAGES: readonly Message[] = []
type Props = { sealedQuery: SealedLiveQuery<Message>; channelId: number; userId: string }

export function Messages({ sealedQuery, channelId, userId }: Props) {
  const refreshQuery = useCallback(() => fetchSealedMessages(channelId), [channelId])
  const { data, status, error, utils } = useLiveQuery(sealedQuery, { refreshQuery })
  // Once the sent message syncs, show only the synced row
  const [messages, addOptimistic] = useOptimistic(data ?? NO_MESSAGES, (current, message: Message) =>
    current.some(({ id }) => id === message.id) ? current : [message, ...current]
  )

  function send(body: string) {
    // The server sets author and timestamp but keeps this id
    const message = { id: crypto.randomUUID(), channel_id: channelId, author_id: userId, body, created_at: new Date() }
    startTransition(async () => {
      addOptimistic(message)
      try {
        const result = await sendMessage(message) // maps channel_id to channelId
        if (result.kind === "committed") await utils.awaitTxId(result.txid, 10_000)
      } catch { /* show "Couldn't confirm the change" */ }
    })
  }

  if (status === "error") return <p role="alert">Live updates stopped: {error.message}</p>
  if (data === undefined) return <p>Loading messages</p>
  return (
    <form action={(form) => send(String(form.get("body")))}>
      <input name="body" required />
      <ul>{messages.map((message) => <li key={message.id}>{message.body}</li>)}</ul>
    </form>
  )
}

Choose the Stack

A live query replaces fetching app data from an API or another sync system. Reuse existing query code, and use the highest layer that fits rather than wiring changes into app state by hand.

Migrating from Electric: Realtime is a drop-in replacement for Electric's role in your stack. Live SQL queries replace shapes, and realtimeCollectionOptions() replaces electricCollectionOptions().

Setup

• New app: neon bootstrap my-app --template realtime-react, then neon deploy in my-app.
• Enable it on the linked branch with neon realtime enable --allowed-origin <app origin>, or declare preview: { realtime: true } in neon.ts (neon config add realtime) and run neon deploy. Child branches inherit it. It's unavailable on Claimable projects until claimed, or outside the supported regions.
• Tables need a stable replica identity; a primary key is enough.
• Environment: neon env pull --service postgres --service realtime writes DATABASE_URL, NEON_REALTIME_URL and NEON_REALTIME_SECRET. Expose only the URL to the browser, under your framework's public prefix (like VITE_). url options take NEON_REALTIME_URL; db takes the database name from DATABASE_URL.
• Install @neon/realtime and the packages chosen above. Use these SDKs, not the still-evolving WebSocket protocol.

Define and Seal Queries

Read references/queries.md before writing query or sealing code, including Kysely and server functions.

• Read-only and deterministic. A raw query is a single SELECT with no ; and $1 placeholders. It can't call now() or gen_random_uuid(), so pass such values as parameters, wrapping every value except strings, numbers, booleans, bigints and null in a pgParam helper (pgParam.timestamptz(date)).
• Authorize in the query. Check the session before sealing, and join through your membership tables so revoked access drops out. Any web framework auth works, including Managed Better Auth, but not RLS yet. See Authorization.
• A sealed query is a bearer token. Keep it out of URLs, logs and persistent storage, and never fill its parameters from unchecked input.
• Check a query before wiring it in: neon realtime subscribe "SELECT ..." prints the initial result, then each transaction's changes, until you stop it. With --output json, each change prints a full snapshot. Set debugMode on createRealtime for full database errors (development only).
• Sealed queries expire. Pass refreshQuery to the bindings or call renew(), sealing the same query and parameters, or the subscription errors. New parameters need a new sealed query and subscription. In Next.js, renew from a Route Handler, because server actions run one at a time.

Subscribe

Read references/reactivity.md before writing React or TanStack DB code. Read references/subscribing.md before subscribing directly with client.subscribe(sealed) (getSnapshot, onChange, onStateChange), or from agents and workers, which add url to createRealtime and await realtime.subscribe(query) to seal in-process.

• One database per client. The first sealed query binds the connection to its db.
• Select a stable, unique key for every row and key rows by it, including TanStack DB's getKey: usually the primary key, the grouped columns for aggregates, or the combined keys for joins that repeat a row. Never use rowId, which every rows update invalidates.
• error is final, even after renew(). Fetch a fresh sealed query and subscribe again, with a new client if the connection failed. Watch onStateChange on direct subscriptions; useLiveQuery() reports errors through status, not by throwing or suspending.
• When the session changes, leave with a full page load. It drops the Realtime client, any TanStack DbClient and the previous user's rows. The hook retries a failed renewal every second, so stop renewing once one fails as signed out. Check on every renewal and write that the session's user is the one the page was loaded for, or a write from the old page lands in the new user's account. See When the session changes.

Optimistic Writes

Realtime has no write path, so writes keep your backend's usual auth. Read references/mutations.md before writing mutations, for each layer.

• Return the txid from the write itself: .returning({ txid: sql<string>`pg_current_xact_id()::text` }), in one round trip on any Postgres driver. Write a batch in one statement, so there's one txid. Never open db.transaction() just to select pg_current_xact_id(): that's four round trips holding a pooled connection. When a write genuinely needs several statements, put the txid in the RETURNING of a write that always changes a row.
• Always pass awaitTxId() a timeout: it keeps waiting through reconnects and renewals, and never settles if the txid doesn't reach the query.
• A write that changes no rows has no txid, so skip awaitTxId() and let the optimistic state drop.

Server-Side Rendering

Read references/ssr.md before rendering live queries on the server, for Next.js and TanStack Start.

• Create the client in a useState initializer rather than at module level, render initialData as live rows without a loading state, and never share a TanStack DbClient between requests.
• Keep row shapes identical on both sides. JSON.stringify turns dates into strings, and int8 and numeric arrive as strings.

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