diff --git a/app/backend/src/lib/realtime.ts b/app/backend/src/lib/realtime.ts
new file mode 100644
index 0000000..2dfdafb
--- /dev/null
+++ b/app/backend/src/lib/realtime.ts
@@ -0,0 +1,171 @@
+import type { FastifyReply, FastifyRequest } from 'fastify';
+import type { NotificationType, Prisma } from '@prisma/client';
+import { redis } from '../redis.js';
+import { prisma } from '../db.js';
+import { sendPushToUser } from './push.js';
+
+const REALTIME_CHANNEL = 'teknav:realtime';
+const ACTIVE_GUESTS_KEY = 'visitors:guests';
+const ACTIVE_USERS_KEY = 'visitors:users';
+const COMMENTS_STATS_KEY = 'stats:comments';
+const ACTIVE_WINDOW_MS = 5 * 60 * 1000;
+
+export type RealtimeEvent =
+  | { event: 'notification'; userId: string; data: unknown }
+  | { event: 'activity'; data: unknown }
+  | { event: 'visitor_update'; data: { count: number; guests: number; users: number; commentsPerMin: number } }
+  | { event: 'view_update'; data: unknown };
+
+export async function publishRealtime(event: RealtimeEvent) {
+  await redis.publish(REALTIME_CHANNEL, JSON.stringify(event));
+}
+
+export async function createNotification(userId: string, type: NotificationType, payload: Prisma.InputJsonValue) {
+  const row = await prisma.notification.create({ data: { userId, type, payload } });
+  const data = publicNotification(row);
+  await publishRealtime({ event: 'notification', userId, data });
+  sendPushToUser(userId, type, payload as Record<string, unknown>).catch(() => {});
+  return data;
+}
+
+export function publicNotification(row: {
+  id: string;
+  type: NotificationType;
+  payload: Prisma.JsonValue;
+  read: boolean;
+  createdAt: Date;
+}) {
+  return {
+    id: row.id,
+    type: row.type,
+    payload: row.payload,
+    read: row.read,
+    createdAt: row.createdAt.toISOString(),
+  };
+}
+
+export function setupSse(reply: FastifyReply) {
+  reply.hijack();
+  reply.raw.writeHead(200, {
+    'Content-Type': 'text/event-stream; charset=utf-8',
+    'Cache-Control': 'no-cache, no-transform',
+    Connection: 'keep-alive',
+    'X-Accel-Buffering': 'no',
+  });
+  reply.raw.write('retry: 5000\n\n');
+}
+
+export function writeSse(reply: FastifyReply, event: string, data: unknown) {
+  reply.raw.write(`event: ${event}\n`);
+  reply.raw.write(`data: ${JSON.stringify(data)}\n\n`);
+}
+
+export async function subscribeRealtime(
+  reply: FastifyReply,
+  filter: (event: RealtimeEvent) => boolean,
+) {
+  const subscriber = redis.duplicate();
+  await subscriber.connect();
+  await subscriber.subscribe(REALTIME_CHANNEL);
+  const onMessage = (_channel: string, message: string) => {
+    try {
+      const event = JSON.parse(message) as RealtimeEvent;
+      if (filter(event)) writeSse(reply, event.event, event.data);
+    } catch {
+      // Ignore malformed pub/sub payloads.
+    }
+  };
+  subscriber.on('message', onMessage);
+  const heartbeat = setInterval(() => {
+    reply.raw.write(': heartbeat\n\n');
+  }, 25_000);
+  reply.raw.on('close', () => {
+    clearInterval(heartbeat);
+    subscriber.off('message', onMessage);
+    subscriber.quit().catch(() => undefined);
+  });
+}
+
+export async function recordActiveVisitor(req: FastifyRequest) {
+  if (!req.url.startsWith('/api/') || req.url.includes('/stream')) return;
+  const now = Date.now();
+  if (req.session?.userId) {
+    await redis.zadd(ACTIVE_USERS_KEY, now, req.session.userId.toString());
+    await redis.pexpire(ACTIVE_USERS_KEY, ACTIVE_WINDOW_MS * 2);
+  } else {
+    const ip = req.ip || 'unknown';
+    await redis.zadd(ACTIVE_GUESTS_KEY, now, ip);
+    await redis.pexpire(ACTIVE_GUESTS_KEY, ACTIVE_WINDOW_MS * 2);
+  }
+}
+
+export async function publishVisitorCount() {
+  const now = Date.now();
+  const cutoff = now - ACTIVE_WINDOW_MS;
+  const commentCutoff = now - 60 * 1000;
+  
+  await redis.zremrangebyscore(ACTIVE_GUESTS_KEY, 0, cutoff);
+  await redis.zremrangebyscore(ACTIVE_USERS_KEY, 0, cutoff);
+  await redis.zremrangebyscore(COMMENTS_STATS_KEY, 0, commentCutoff);
+  
+  const guests = await redis.zcard(ACTIVE_GUESTS_KEY);
+  const users = await redis.zcard(ACTIVE_USERS_KEY);
+  const commentsPerMin = await redis.zcard(COMMENTS_STATS_KEY);
+  const count = guests + users;
+  
+  await publishRealtime({ event: 'visitor_update', data: { count, guests, users, commentsPerMin } });
+  return { count, guests, users, commentsPerMin };
+}
+
+export async function recordCommentEvent() {
+  const now = Date.now();
+  await redis.zadd(COMMENTS_STATS_KEY, now, `${now}-${Math.random()}`);
+  await redis.pexpire(COMMENTS_STATS_KEY, 60 * 1000 * 2);
+}
+
+export async function notifyFollowersOnPublish(article: {
+  id: string;
+  slug: string;
+  title: string;
+  author: { userId: string | null; name: string };
+  category?: { slug: string; name?: string } | null;
+}) {
+  const [writerFollows, topicFollows] = await Promise.all([
+    article.author.userId
+      ? prisma.writerFollow.findMany({
+          where: { writerId: article.author.userId },
+          select: { followerId: true },
+        })
+      : Promise.resolve([]),
+    article.category?.slug
+      ? prisma.topicFollow.findMany({
+          where: { topic: article.category.slug },
+          select: { userId: true },
+        })
+      : Promise.resolve([]),
+  ]);
+  const userIds = new Set([
+    ...writerFollows.map((follow) => follow.followerId),
+    ...topicFollows.map((follow) => follow.userId),
+  ]);
+  await Promise.all([...userIds].map((userId) => createNotification(userId, 'new_article', {
+    articleId: article.id,
+    articleSlug: article.slug,
+    articleTitle: article.title,
+    actorName: article.author.name,
+    topic: article.category?.slug ?? null,
+    topicName: article.category?.name ?? null,
+  })));
+}
+
+export async function notifyEditorsOnSubmit(article: { slug: string, title: string, authorName: string }) {
+  const editors = await prisma.user.findMany({
+    where: { role: { in: ['admin', 'editor', 'reviewer'] } },
+    select: { id: true }
+  });
+  await Promise.all(editors.map(e => createNotification(e.id.toString(), 'review_submitted', {
+    articleSlug: article.slug,
+    articleTitle: article.title,
+    actorName: article.authorName,
+  })));
+}