個人開発SaaSの技術スタック選定：2025年版の判断基準

// Next.js 15のServer Actions - 個人SaaSで典型的なパターン
'use server'

import { revalidatePath } from 'next/cache'
import { redirect } from 'next/navigation'
import { auth } from '@/lib/auth'
import { db } from '@/lib/db'

export async function createProject(formData: FormData) {
  const session = await auth()
  if (!session?.user) redirect('/login')

  const name = formData.get('name') as string
  const description = formData.get('description') as string

  const project = await db.project.create({
    data: {
      name,
      description,
      ownerId: session.user.id,
    },
  })

  revalidatePath('/dashboard')
  redirect(`/projects/${project.id}`)
}

// Astroのコンテンツコレクション - ブログ型SaaSに最適
// src/content/config.ts
import { z, defineCollection } from 'astro:content'

const blogCollection = defineCollection({
  type: 'content',
  schema: z.object({
    title: z.string(),
    publishedAt: z.date(),
    tags: z.array(z.string()),
    draft: z.boolean().default(false),
  }),
})

export const collections = { blog: blogCollection }

// Honoを使ったAPI（Cloudflare WorkersやBunで実行可能）
import { Hono } from 'hono'
import { zValidator } from '@hono/zod-validator'
import { z } from 'zod'

const app = new Hono()

const createUserSchema = z.object({
  name: z.string().min(1).max(100),
  email: z.string().email(),
})

app.post('/api/users',
  zValidator('json', createUserSchema),
  async (c) => {
    const { name, email } = c.req.valid('json')

    // データベース処理
    const user = await createUser({ name, email })

    return c.json({ success: true, data: user }, 201)
  }
)

export default app

// tRPCのルーター定義（Next.jsと完全な型共有）
import { z } from 'zod'
import { createTRPCRouter, protectedProcedure } from '@/lib/trpc'

export const projectRouter = createTRPCRouter({
  list: protectedProcedure.query(async ({ ctx }) => {
    return ctx.db.project.findMany({
      where: { ownerId: ctx.session.user.id },
      orderBy: { createdAt: 'desc' },
    })
  }),

  create: protectedProcedure
    .input(z.object({ name: z.string().min(1), description: z.string() }))
    .mutation(async ({ ctx, input }) => {
      return ctx.db.project.create({
        data: { ...input, ownerId: ctx.session.user.id },
      })
    }),
})

// Clerk を使った認証（最もシンプル）
// middleware.ts
import { clerkMiddleware, createRouteMatcher } from '@clerk/nextjs/server'

const isProtectedRoute = createRouteMatcher(['/dashboard(.*)', '/api/(.*)'])

export default clerkMiddleware((auth, req) => {
  if (isProtectedRoute(req)) auth().protect()
})

// app/dashboard/page.tsx
import { auth, currentUser } from '@clerk/nextjs/server'

export default async function DashboardPage() {
  const { userId } = auth()
  const user = await currentUser()

  if (!userId || !user) return null

  return (
    <div>
      <h1>こんにちは、{user.firstName}さん</h1>
    </div>
  )
}

// Auth.js (NextAuth) を使った認証（カスタマイズ性が高い）
// app/api/auth/[...nextauth]/route.ts
import NextAuth from 'next-auth'
import GitHub from 'next-auth/providers/github'
import { PrismaAdapter } from '@auth/prisma-adapter'
import { prisma } from '@/lib/db'

export const { handlers, auth, signIn, signOut } = NextAuth({
  adapter: PrismaAdapter(prisma),
  providers: [GitHub],
  callbacks: {
    session: ({ session, user }) => ({
      ...session,
      user: { ...session.user, id: user.id },
    }),
  },
})

// Fly.ioのDocker設定（Honoサーバーのデプロイ例）
// Dockerfile
// FROM oven/bun:1 AS base
// WORKDIR /usr/src/app
//
// FROM base AS install
// COPY package.json bun.lockb ./
// RUN bun install --frozen-lockfile
//
// FROM base AS release
// COPY --from=install /usr/src/app/node_modules node_modules
// COPY . .
// USER bun
// EXPOSE 3000/tcp
// ENTRYPOINT [ "bun", "run", "src/index.ts" ]

// fly.toml
// app = "my-saas-api"
// primary_region = "nrt"  // 東京リージョン
//
// [http_service]
// internal_port = 3000
// force_https = true
// auto_stop_machines = true
// auto_start_machines = true
// min_machines_running = 0  // コスト削減：使われていない時は0台に

// next.config.ts - Vercelへのデプロイ最適化
import type { NextConfig } from 'next'

const nextConfig: NextConfig = {
  // 静的ページの最大限の活用
  experimental: {
    // PPR (Partial Prerendering) - Next.js 15の実験的機能
    ppr: true,
  },
  images: {
    // 外部画像ドメインの許可
    remotePatterns: [
      { protocol: 'https', hostname: '**.supabase.co' },
    ],
  },
}

export default nextConfig