Newsletter platform on Next.js 16 (App Router), MySQL 8 and Better Auth

import { drizzle } from "drizzle-orm/mysql2";
import mysql from "mysql2/promise";

// ponytail: single module-level pool; the runtime + mysql2's pool handle concurrency,
// so no globalThis singleton dance needed.
const pool = mysql.createPool(process.env.DATABASE_URL!);

export const db = drizzle({ client: pool });

import { boolean, mysqlTable, text, timestamp, varchar } from "drizzle-orm/mysql-core";

export const user = mysqlTable("user", {
  id: varchar("id", { length: 255 }).primaryKey(),
  name: text("name").notNull(),
  email: varchar("email", { length: 255 }).notNull().unique(),
  emailVerified: boolean("email_verified").notNull().default(false),
  image: text("image"),
  createdAt: timestamp("created_at").notNull().defaultNow(),
  updatedAt: timestamp("updated_at").notNull().defaultNow(),
});

export const session = mysqlTable("session", {
  id: varchar("id", { length: 255 }).primaryKey(),
  expiresAt: timestamp("expires_at").notNull(),
  token: varchar("token", { length: 255 }).notNull().unique(),
  createdAt: timestamp("created_at").notNull().defaultNow(),
  updatedAt: timestamp("updated_at").notNull(),
  ipAddress: text("ip_address"),
  userAgent: text("user_agent"),
  userId: varchar("user_id", { length: 255 })
    .notNull()
    .references(() => user.id, { onDelete: "cascade" }),
});

export const account = mysqlTable("account", {
  id: varchar("id", { length: 255 }).primaryKey(),
  accountId: text("account_id").notNull(),
  providerId: text("provider_id").notNull(),
  userId: varchar("user_id", { length: 255 })
    .notNull()
    .references(() => user.id, { onDelete: "cascade" }),
  accessToken: text("access_token"),
  refreshToken: text("refresh_token"),
  idToken: text("id_token"),
  accessTokenExpiresAt: timestamp("access_token_expires_at"),
  refreshTokenExpiresAt: timestamp("refresh_token_expires_at"),
  scope: text("scope"),
  password: text("password"),
  createdAt: timestamp("created_at").notNull().defaultNow(),
  updatedAt: timestamp("updated_at").notNull(),
});

export const verification = mysqlTable("verification", {
  id: varchar("id", { length: 255 }).primaryKey(),
  identifier: text("identifier").notNull(),
  value: text("value").notNull(),
  expiresAt: timestamp("expires_at").notNull(),
  createdAt: timestamp("created_at").notNull().defaultNow(),
  updatedAt: timestamp("updated_at").notNull().defaultNow(),
});

// 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";
import * as authSchema from "@/db/auth-schema";

export const auth = betterAuth({
  // Drizzle adapter over the shared client. The schema is passed HERE (not into
  // drizzle()) — it is the only consumer that needs it, so the db client stays
  // schema-less. ponytail: do NOT enable experimental.joins; it is the one option
  // that would make the adapter reach into db._.fullSchema.
  // ponytail: usePlural stays false (the default) — with it true Better Auth would
  // look for `sessions`/`accounts` and could bind to the analytics/ledger app-type tables.
  database: drizzleAdapter(db, { provider: "mysql", schema: authSchema }),
  // 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;

// 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);

// 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*"],
};

// === file: src/db/schema.ts ===
import { relations, sql } from "drizzle-orm";
import {
  check,
  index,
  mysqlTable,
  text,
  timestamp,
  unique,
  varchar,
} from "drizzle-orm/mysql-core";
// Better Auth owns identity; we only reference its `user` table by id.
import { user } from "./auth-schema";

export type SubscriberStatus = "subscribed" | "unsubscribed" | "bounced";
export type CampaignStatus = "draft" | "scheduled" | "sent";
export type CampaignSendStatus =
  | "queued"
  | "delivered"
  | "opened"
  | "bounced";

/** An email address on someone's audience. Owned by the user who collected it;
 *  status walks the deliverability lifecycle. The owner+email unique stops the
 *  same address landing on one owner's audience twice. */
export const subscribers = mysqlTable(
  "subscribers",
  {
    id: varchar("id", { length: 36 }).primaryKey(),
    // Better Auth's user.id is varchar(255) on MySQL — match it, don't recast.
    ownerId: varchar("owner_id", { length: 255 })
      .notNull()
      .references(() => user.id, { onDelete: "cascade" }),
    // Part of the owner+email unique below — MySQL can't index unbounded text.
    email: varchar("email", { length: 255 }).notNull(),
    status: varchar("status", { length: 32 })
      .$type<SubscriberStatus>()
      .notNull()
      .default("subscribed"),
    createdAt: timestamp("created_at").notNull().defaultNow(),
  },
  (t) => [
    unique("subscribers_owner_email_unique").on(t.ownerId, t.email),
    index("idx_subscriber_owner").on(t.ownerId),
    check(
      "subscribers_status_check",
      sql`${t.status} in ('subscribed','unsubscribed','bounced')`,
    ),
  ],
);

/** A named segment of an owner's audience (e.g. "Weekly digest"). */
export const lists = mysqlTable(
  "lists",
  {
    id: varchar("id", { length: 36 }).primaryKey(),
    ownerId: varchar("owner_id", { length: 255 })
      .notNull()
      .references(() => user.id, { onDelete: "cascade" }),
    name: text("name").notNull(),
    createdAt: timestamp("created_at").notNull().defaultNow(),
  },
  (t) => [index("idx_list_owner").on(t.ownerId)],
);

/** list <-> subscriber join. The composite unique is the membership identity —
 *  a subscriber is on a list at most once. */
export const listSubscriptions = mysqlTable(
  "list_subscriptions",
  {
    id: varchar("id", { length: 36 }).primaryKey(),
    listId: varchar("list_id", { length: 36 })
      .notNull()
      .references(() => lists.id, { onDelete: "cascade" }),
    subscriberId: varchar("subscriber_id", { length: 36 })
      .notNull()
      .references(() => subscribers.id, { onDelete: "cascade" }),
    createdAt: timestamp("created_at").notNull().defaultNow(),
  },
  (t) => [
    unique("list_subscriptions_list_subscriber_unique").on(
      t.listId,
      t.subscriberId,
    ),
    index("idx_list_subscription_subscriber").on(t.subscriberId),
  ],
);

/** A broadcast targeting a list. status walks the lifecycle; scheduledAt is the
 *  send time once status is 'scheduled'. */
export const campaigns = mysqlTable(
  "campaigns",
  {
    id: varchar("id", { length: 36 }).primaryKey(),
    listId: varchar("list_id", { length: 36 })
      .notNull()
      .references(() => lists.id, { onDelete: "cascade" }),
    subject: text("subject").notNull(),
    status: varchar("status", { length: 32 })
      .$type<CampaignStatus>()
      .notNull()
      .default("draft"),
    scheduledAt: timestamp("scheduled_at"),
    createdAt: timestamp("created_at").notNull().defaultNow(),
  },
  (t) => [
    index("idx_campaign_list").on(t.listId),
    check(
      "campaigns_status_check",
      sql`${t.status} in ('draft','scheduled','sent')`,
    ),
  ],
);

/** One row per (campaign, subscriber) send attempt. status walks delivery; the
 *  campaign index drives the per-campaign delivery/open rollup. */
export const campaignSends = mysqlTable(
  "campaign_sends",
  {
    id: varchar("id", { length: 36 }).primaryKey(),
    campaignId: varchar("campaign_id", { length: 36 })
      .notNull()
      .references(() => campaigns.id, { onDelete: "cascade" }),
    subscriberId: varchar("subscriber_id", { length: 36 })
      .notNull()
      .references(() => subscribers.id, { onDelete: "cascade" }),
    status: varchar("status", { length: 32 })
      .$type<CampaignSendStatus>()
      .notNull()
      .default("queued"),
    sentAt: timestamp("sent_at"),
  },
  (t) => [
    // Drives the "delivery/open stats for this campaign" rollup query.
    index("idx_send_campaign").on(t.campaignId),
    check(
      "campaign_sends_status_check",
      sql`${t.status} in ('queued','delivered','opened','bounced')`,
    ),
  ],
);

export const subscribersRelations = relations(subscribers, ({ one, many }) => ({
  owner: one(user, { fields: [subscribers.ownerId], references: [user.id] }),
  listSubscriptions: many(listSubscriptions),
  sends: many(campaignSends),
}));

export const listsRelations = relations(lists, ({ one, many }) => ({
  owner: one(user, { fields: [lists.ownerId], references: [user.id] }),
  listSubscriptions: many(listSubscriptions),
  campaigns: many(campaigns),
}));

export const listSubscriptionsRelations = relations(
  listSubscriptions,
  ({ one }) => ({
    list: one(lists, {
      fields: [listSubscriptions.listId],
      references: [lists.id],
    }),
    subscriber: one(subscribers, {
      fields: [listSubscriptions.subscriberId],
      references: [subscribers.id],
    }),
  }),
);

export const campaignsRelations = relations(campaigns, ({ one, many }) => ({
  list: one(lists, {
    fields: [campaigns.listId],
    references: [lists.id],
  }),
  sends: many(campaignSends),
}));

export const campaignSendsRelations = relations(campaignSends, ({ one }) => ({
  campaign: one(campaigns, {
    fields: [campaignSends.campaignId],
    references: [campaigns.id],
  }),
  subscriber: one(subscribers, {
    fields: [campaignSends.subscriberId],
    references: [subscribers.id],
  }),
}));

import { drizzle } from "drizzle-orm/mysql2";
import mysql from "mysql2/promise";

// Serverless: a small pool per short-lived instance — many instances × a big pool exhausts MySQL.
export const pool = mysql.createPool({ uri: process.env.DATABASE_URL!, connectionLimit: 2 });
export const db = drizzle({ client: pool });

import { drizzle } from "drizzle-orm/mysql2";
import mysql from "mysql2/promise";

// Long-running process: a real, reused pool (mysql2 manages idle recycling).
export const pool = mysql.createPool({ uri: process.env.DATABASE_URL!, connectionLimit: 10 });
export const db = drizzle({ client: pool });

import { drizzle } from "drizzle-orm/planetscale-serverless";
import { Client } from "@planetscale/database";

// Edge/Workers have NO TCP sockets, so mysql2 cannot run here. PlanetScale's HTTP driver
// speaks MySQL over fetch — the client that works on Workers (the MySQL analog of Neon's HTTP driver).
const client = new Client({ url: process.env.DATABASE_URL! });
export const db = drizzle({ client });