⚡ Bolt: Implement Prisma Client singleton

[davidraehles]

💡 What: This optimization centralizes the Prisma Client into a singleton instance located in backend/src/lib/prisma.ts. Previously, multiple new PrismaClient() calls were present in different route files, each creating its own connection pool. Additionally, pre-existing TypeScript errors in notes.ts were fixed to ensure the project builds correctly with Express 5.

🎯 Why: Creating multiple Prisma Client instances leads to multiple database connection pools. This is inefficient as it consumes unnecessary memory on the server and can quickly lead to database connection exhaustion, especially under load or in environments with connection limits.

📊 Measured Improvement: While a numerical baseline could not be established due to the lack of a test database and load-testing tools in the environment, the architectural benefit is well-documented. By moving to a singleton, we ensure that only one connection pool is created for the entire application, which is the recommended best practice for Prisma in Node.js applications. This change reduces memory overhead and prevents potential database connection leaks. Verified that new PrismaClient() now only appears once in the codebase and that the backend builds successfully.

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PR created automatically by Jules for task 1542024686322854175 started by @davidraehles

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[Copilot]

Pull request overview

This PR implements a Prisma Client singleton pattern to prevent multiple database connection pools from being created across different route files. The changes consolidate all Prisma Client instantiation into a single module (backend/src/lib/prisma.ts) and update route files to import this shared instance. Additionally, TypeScript compilation errors in Express 5 route handlers were fixed by explicitly casting req.params values to string.

Changes:

• Created centralized Prisma Client singleton in backend/src/lib/prisma.ts
• Updated auth.ts and notes.ts routes to use the singleton instance
• Fixed Express 5 TypeScript typing issues by casting route parameters to string
• Added pnpm lockfile for dependency management

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
backend/src/lib/prisma.ts	New file introducing Prisma Client singleton pattern
backend/src/routes/notes.ts	Replaced local PrismaClient instantiation with singleton import; fixed TypeScript type casting for req.params.id
backend/src/routes/auth.ts	Replaced local PrismaClient instantiation with singleton import
backend/pnpm-lock.yaml	Added pnpm lockfile for dependency management
.jules/bolt.md	Added documentation explaining the rationale for Prisma singleton and Express 5 type casting

Files not reviewed (1)

• backend/pnpm-lock.yaml: Language not supported

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[Copilot]

This PR adds a pnpm-lock.yaml file, but backend/package-lock.json still exists in the repository. Having both npm and pnpm lockfiles can lead to dependency conflicts and inconsistent installations. You should remove package-lock.json and commit that deletion in this PR to ensure the project uses pnpm exclusively.

[davidraehles]

Removed pnpm-lock.yaml from the branch.

[google-labs-jules]

I have removed the backend/pnpm-lock.yaml file from the branch as requested.

[Copilot]

The Prisma Client singleton implementation is missing recommended development environment handling. According to Prisma best practices, in development mode with hot-reloading (nodemon), you should prevent creating multiple instances by caching the client on the global object. This prevents "too many clients" errors during development. Consider implementing the pattern recommended in Prisma's documentation that checks for globalThis.prisma and reuses it in development environments.

Suggested change

	const prisma = new PrismaClient();
	declare global {
	// eslint-disable-next-line no-var
	var prisma: PrismaClient | undefined;
	}
	const prisma = globalThis.prisma ?? new PrismaClient();
	if (process.env.NODE_ENV !== 'production') {
	globalThis.prisma = prisma;
	}

[davidraehles]

Implemented the standard Prisma singleton pattern with globalThis caching for development environments to prevent multiple client instances during hot reload.

[google-labs-jules]

I've updated the Prisma singleton implementation to use the standard pattern with globalThis caching. This will prevent multiple instances from being created during hot reloads in development.

[Copilot]

Consider adding graceful shutdown handling for the Prisma Client. When the application terminates, the database connections should be properly closed using prisma.$disconnect(). This should be added to the server.ts file with process event handlers for SIGINT and SIGTERM to ensure clean shutdowns and prevent connection leaks.

Suggested change

	if (typeof process !== 'undefined' && typeof process.on === 'function') {
	const gracefulShutdown = async (signal: string) => {
	try {
	await prisma.$disconnect();
	} catch (error) {
	console.error(`Error disconnecting PrismaClient on ${signal}:`, error);
	} finally {
	// Let the process exit naturally after cleanup
	}
	};
	process.on('beforeExit', () => {
	gracefulShutdown('beforeExit');
	});
	process.on('SIGINT', () => {
	gracefulShutdown('SIGINT').finally(() => {
	process.exit(0);
	});
	});
	process.on('SIGTERM', () => {
	gracefulShutdown('SIGTERM').finally(() => {
	process.exit(0);
	});
	});
	}

[davidraehles]

Added graceful shutdown handlers for SIGINT and SIGTERM that disconnect the Prisma client before process exit.