LMS (learning platform) on Next.js 16 (App Router) + Postgres (Neon) + Better Auth

✓ Verified 2026-06-21 · next 16.2.9 · postgres 3.4.9 · better-auth 1.6.20

Type-checked against the real SDKs, migration applied to a live Postgres, pooling tested — then tracked for upstream drift and re-verified when it moves. How we verify →

What you're getting

Setup

bun add next react react-dom drizzle-orm postgres better-auth

Environment variables:

Apply the schema: bunx drizzle-kit push

Initialization

src/lib/db.ts — Database client

import { drizzle } from "drizzle-orm/postgres-js";
import postgres from "postgres";

// Neon pooled endpoint = PgBouncer transaction mode → prepared statements off.
// ponytail: single module-level client; the serverless runtime + PgBouncer do
// the pooling, so no custom pool/globalThis singleton dance needed.
const client = postgres(process.env.DATABASE_URL!, { prepare: false });

export const db = drizzle({ client });

src/lib/auth.ts — Auth instance

// Better Auth instance (self-hosted, Next.js 16 (App Router)).
import { betterAuth } from "better-auth";
import { drizzleAdapter } from "better-auth/adapters/drizzle";
// Reuse the SAME postgres-js/Drizzle client the db slice exported in
// src/lib/db.ts — Better Auth shares the pooled `DATABASE_URL` connection.
import { db } from "./db";

export const auth = betterAuth({
  // Drizzle adapter over the shared client; provider "pg" => Postgres DDL
  // for Better Auth's own user/session/account/verification tables.
  database: drizzleAdapter(db, { provider: "pg" }),
  // ponytail: email+password is the shortest real auth that works out of
  // the box — add socialProviders / plugins here when the app needs them.
  emailAndPassword: { enabled: true },
  secret: process.env.BETTER_AUTH_SECRET,
  baseURL: process.env.BETTER_AUTH_URL,
});

export type Session = typeof auth.$Infer.Session;

app/api/auth/[...all]/route.ts — Route handler

// Mount Better Auth on Next's route layer.
import { toNextJsHandler } from "better-auth/next-js";
import { auth } from "@/lib/auth";

export const { GET, POST } = toNextJsHandler(auth);

proxy.ts — Route protection

// Session-protection proxy for Next.js 16 (App Router) (Next 16 renamed middleware.ts → proxy.ts).
// ponytail: getSessionCookie only checks the cookie EXISTS (no DB hit at
// the Edge runtime) — do the real auth.api.getSession() check inside
// protected Server Components / route handlers. This just bounces
// logged-out users before render.
import { NextResponse, type NextRequest } from "next/server";
import { getSessionCookie } from "better-auth/cookies";

export function proxy(request: NextRequest) {
  const sessionCookie = getSessionCookie(request);
  if (!sessionCookie) {
    return NextResponse.redirect(new URL("/sign-in", request.url));
  }
  return NextResponse.next();
}

export const config = {
  // ponytail: guard the SaaS app surface; widen the matcher per app-type.
  matcher: ["/dashboard/:path*", "/settings/:path*"],
};

LMS schema: courses, modules, lessons, enrollments & progress

import { relations, sql } from "drizzle-orm";
import {
  check,
  index,
  integer,
  pgTable,
  text,
  timestamp,
  unique,
  uuid,
} from "drizzle-orm/pg-core";
// Better Auth owns identity; we only reference its `user` table by id.
import { user } from "./auth-schema";

export type CourseStatus = "draft" | "published" | "archived";
export type LessonContentType = "video" | "text" | "quiz";
export type ProgressStatus = "not_started" | "in_progress" | "completed";

/** Catalog root. Each course has one instructor (a Better Auth user). */
export const courses = pgTable(
  "courses",
  {
    id: uuid("id").primaryKey().defaultRandom(),
    slug: text("slug").notNull().unique(),
    title: text("title").notNull(),
    // Better Auth's user.id is text — match it, don't recast.
    instructorId: text("instructor_id")
      .notNull()
      .references(() => user.id, { onDelete: "cascade" }),
    status: text("status")
      .$type<CourseStatus>()
      .notNull()
      .default("draft"),
    createdAt: timestamp("created_at", { withTimezone: true })
      .notNull()
      .defaultNow(),
  },
  (t) => [
    index("idx_course_slug").on(t.slug),
    index("idx_course_instructor").on(t.instructorId),
    check(
      "courses_status_check",
      sql`${t.status} in ('draft','published','archived')`,
    ),
  ],
);

/** Ordered sections within a course. position drives curriculum order. */
export const modules = pgTable(
  "modules",
  {
    id: uuid("id").primaryKey().defaultRandom(),
    courseId: uuid("course_id")
      .notNull()
      .references(() => courses.id, { onDelete: "cascade" }),
    title: text("title").notNull(),
    position: integer("position").notNull().default(0),
    createdAt: timestamp("created_at", { withTimezone: true })
      .notNull()
      .defaultNow(),
  },
  (t) => [index("idx_module_course").on(t.courseId, t.position)],
);

/** Leaf content unit. contentType selects how the lesson renders/plays. */
export const lessons = pgTable(
  "lessons",
  {
    id: uuid("id").primaryKey().defaultRandom(),
    moduleId: uuid("module_id")
      .notNull()
      .references(() => modules.id, { onDelete: "cascade" }),
    title: text("title").notNull(),
    position: integer("position").notNull().default(0),
    contentType: text("content_type")
      .$type<LessonContentType>()
      .notNull()
      .default("text"),
    createdAt: timestamp("created_at", { withTimezone: true })
      .notNull()
      .defaultNow(),
  },
  (t) => [
    index("idx_lesson_module").on(t.moduleId, t.position),
    check(
      "lessons_content_type_check",
      sql`${t.contentType} in ('video','text','quiz')`,
    ),
  ],
);

/** course <-> student join. The composite unique is the enrollment identity. */
export const enrollments = pgTable(
  "enrollments",
  {
    id: uuid("id").primaryKey().defaultRandom(),
    courseId: uuid("course_id")
      .notNull()
      .references(() => courses.id, { onDelete: "cascade" }),
    studentId: text("student_id")
      .notNull()
      .references(() => user.id, { onDelete: "cascade" }),
    enrolledAt: timestamp("enrolled_at", { withTimezone: true })
      .notNull()
      .defaultNow(),
  },
  (t) => [
    unique("enrollments_course_student_unique").on(t.courseId, t.studentId),
    // Drives the learner's "my courses" list.
    index("idx_enrollment_student").on(t.studentId),
  ],
);

/** Per-lesson learner state. The composite unique is one row per student+lesson. */
export const lessonProgress = pgTable(
  "lesson_progress",
  {
    id: uuid("id").primaryKey().defaultRandom(),
    lessonId: uuid("lesson_id")
      .notNull()
      .references(() => lessons.id, { onDelete: "cascade" }),
    studentId: text("student_id")
      .notNull()
      .references(() => user.id, { onDelete: "cascade" }),
    status: text("status")
      .$type<ProgressStatus>()
      .notNull()
      .default("not_started"),
    completedAt: timestamp("completed_at", { withTimezone: true }),
  },
  (t) => [
    unique("lesson_progress_student_lesson_unique").on(
      t.studentId,
      t.lessonId,
    ),
    // Drives the per-learner progress lookup (student + lesson).
    index("idx_progress_student_lesson").on(t.studentId, t.lessonId),
    check(
      "lesson_progress_status_check",
      sql`${t.status} in ('not_started','in_progress','completed')`,
    ),
  ],
);

export const coursesRelations = relations(courses, ({ one, many }) => ({
  instructor: one(user, {
    fields: [courses.instructorId],
    references: [user.id],
  }),
  modules: many(modules),
  enrollments: many(enrollments),
}));

export const modulesRelations = relations(modules, ({ one, many }) => ({
  course: one(courses, {
    fields: [modules.courseId],
    references: [courses.id],
  }),
  lessons: many(lessons),
}));

export const lessonsRelations = relations(lessons, ({ one, many }) => ({
  module: one(modules, {
    fields: [lessons.moduleId],
    references: [modules.id],
  }),
  progress: many(lessonProgress),
}));

export const enrollmentsRelations = relations(enrollments, ({ one }) => ({
  course: one(courses, {
    fields: [enrollments.courseId],
    references: [courses.id],
  }),
  student: one(user, {
    fields: [enrollments.studentId],
    references: [user.id],
  }),
}));

export const lessonProgressRelations = relations(lessonProgress, ({ one }) => ({
  lesson: one(lessons, {
    fields: [lessonProgress.lessonId],
    references: [lessons.id],
  }),
  student: one(user, {
    fields: [lessonProgress.studentId],
    references: [user.id],
  }),
}));

Connection & security

## Next.js 16 ↔ Postgres pooling (Neon pooled endpoint, PgBouncer transaction mode)

Connect through Neon's **pooled** endpoint (`-pooler` host) via `DATABASE_URL`. Serverless
functions are short-lived and concurrent, so PgBouncer in **transaction mode** is what keeps
Postgres' connection ceiling from being blown.

### `prepare: false` is mandatory
Transaction-mode PgBouncer hands each transaction a different backend, so server-side prepared
statements (postgres-js' default) silently break across the pool. Disable them on the client:
`postgres(url, { prepare: false })`. This is also why **Drizzle, not Prisma**, is paired here —
Prisma's prepared-statement reliance is a blocked intersection on this endpoint.

### Connection reuse
- Construct the postgres-js client at **module scope** (`src/lib/db.ts`) so warm function
  instances reuse one socket instead of opening one per request.
- Cap the driver pool small — `max: 1` per instance. The shared pool lives in PgBouncer, not in
  your function; a large per-instance `max` just multiplies idle connections across instances.
- Keep `idle_timeout` ~20s and `connect_timeout` ~10s so frozen instances release backends fast.

### No session-level features
Transaction mode forbids anything that spans transactions on one backend: `LISTEN/NOTIFY`,
session-scoped `SET`, advisory-lock sessions, server-side cursors, and `WITH HOLD`. Need any of
those? Use Neon's **direct** (non-pooled) endpoint for that path only.

### Thresholds
- Drizzle/postgres-js: `prepare: false`, `max: 1`, `idle_timeout: 20`, `connect_timeout: 10`.
- Neon Free pooled budget is ~10k client connections; keep concurrency well under the project's
  `max_connections` (often 100–900 by plan) by leaning on PgBouncer, never on driver pooling.

Decisions & compatibility

Related stacks