File storage with AWS S3

Amazon Simple Storage Service (AWS S3) is an object storage service widely used for storing and retrieving large amounts of data, such as images, videos, backups, and application assets. Neon Object S...

Amazon Simple Storage Service (AWS S3) is an object storage service widely used for storing and retrieving large amounts of data, such as images, videos, backups, and application assets.

Neon now offers native storage

Neon Object Storage is S3-compatible object storage built into the Neon backend. Object storage branches with your database: each branch gets its own isolated namespace, so you can test file uploads in preview branches without touching production. No separate cloud account needed. Use any S3-compatible SDK with your existing Neon credential.

For more information, see Neon Object Storage.

This guide demonstrates how to integrate AWS S3 with Lakebase Postgres by storing file metadata (like the object key and URL) in your database, while using S3 for file storage.

Setup steps

Create a Neon project
1. Navigate to the Neon Console to create a new Neon project.
2. Copy the connection string by clicking the Connect button in the Console nav. For more information, see Connect from any application.
Create an AWS account and S3 bucket
1. Sign up for or log in to your AWS Account.
2. Navigate to the S3 service in the AWS Management Console.
3. Click Create bucket. Provide a unique bucket name (for example, my-neon-app-s3-uploads), select an AWS Region (for example, us-east-1), and configure initial settings.
4. Public Access (for this example): For simplicity in accessing uploaded files via URL in this guide, we'll configure the bucket to allow public read access for objects uploaded with specific permissions. Under Block Public Access settings for this bucket, uncheck "Block all public access". Acknowledge the warning. Making buckets or objects publicly readable carries security risks. For production applications, it's strongly recommended to:Keep buckets private (Block all public access enabled).Use presigned URLs not only for uploads but also for downloads (temporary read access). This guide uses public access for simplicity, but you should implement secure access controls in production.
5. After the bucket is created, navigate to the Permissions tab. Under Bucket Policy, you can set up a policy to allow public read access to objects. For example:
  JSON
```
{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "PublicReadGetObject",
      "Effect": "Allow",
      "Principal": "*",
      "Action": "s3:GetObject",
      "Resource": "arn:aws:s3:::my-neon-app-s3-uploads/*"
    }
  ]
}
```
  Replace my-neon-app-s3-uploads with your actual bucket name.
6. Create IAM user for programmatic access:
  - Navigate to the IAM service in the AWS Console.
  - Go to Users and click Add users.
  - Enter a username (for example, neon-app-s3-user). Select Access key - Programmatic access as the credential type. Click Next: Permissions.
  - Choose Attach policies directly. Search for and select AmazonS3FullAccess.
  - Click Next, then Create user.
  - Click on Create access key.
  - Click Other > Create access key. Copy the Access key ID and Secret access key. These will be used in your application to authenticate with AWS S3.
Configure CORS for client-side uploads
If your application involves uploading files directly from a web browser using the generated presigned URLs, you must configure Cross-Origin Resource Sharing (CORS) on your S3 bucket. CORS rules tell S3 which web domains are allowed to make requests (like PUT requests for uploads) to your bucket. Without proper CORS rules, browser security restrictions will block these direct uploads.
In your S3 bucket settings, navigate to the Permissions tab and find the CORS configuration section. Add the following CORS rules:
JSON
```
[
  {
    "AllowedHeaders": ["*"],
    "AllowedMethods": ["GET", "PUT"],
    "AllowedOrigins": ["*"],
    "ExposeHeaders": [],
    "MaxAgeSeconds": 9000
  }
]
```
This configuration allows any origin (*) to perform GET and PUT requests. In a production environment, you should restrict AllowedOrigins to your application's domain(s) for security.
Create a table in Neon for file metadata
We need a table in the database to store metadata about the objects uploaded to S3.
1. Connect to your database using the Neon SQL Editor or a client like psql. Create a table including the object key, URL, user ID, and timestamp:
  SQL
```
CREATE TABLE IF NOT EXISTS s3_files (
    id SERIAL PRIMARY KEY,
    object_key TEXT NOT NULL UNIQUE, -- Key (path/filename) in S3
    file_url TEXT NOT NULL,          -- Publicly accessible URL (if object is public)
    user_id TEXT NOT NULL,           -- User associated with the file
    upload_timestamp TIMESTAMPTZ DEFAULT NOW()
);
```
2. Run the SQL statement. Add other relevant columns as needed (for example, content_type, size).
Securing metadata with RLS
If you use Row Level Security (RLS), remember to apply appropriate access policies to the s3_files table. This controls who can view or modify the object references stored in the database based on your RLS rules.
Note that these policies apply only to the metadata in the database. Access control for the objects within the S3 bucket itself is managed via S3 bucket policies, IAM permissions, and object ACLs.

Upload files to S3 and store metadata in Neon

The recommended pattern for client-side uploads to S3 involves presigned upload URLs. Your backend generates a temporary URL that the client uses to upload the file directly to S3. Afterwards, your backend saves the file's metadata to Neon.

This requires two backend endpoints:

/presign-upload: Generates the temporary presigned URL.
/save-metadata: Records the metadata in Neon after the client confirms successful upload.

We'll use Hono for the server, @aws-sdk/client-s3 and @aws-sdk/s3-request-presigner for S3 interaction, and @neondatabase/serverless for Neon.

First, install the necessary dependencies:

Bash

npm install @aws-sdk/client-s3 @aws-sdk/s3-request-presigner @neondatabase/serverless @hono/node-server hono dotenv

Create a .env file:

Bash

# AWS S3 Credentials & Config
AWS_ACCESS_KEY_ID=your_iam_user_access_key_id
AWS_SECRET_ACCESS_KEY=your_iam_user_secret_access_key
AWS_REGION=your_s3_bucket_region # for example, us-east-1
S3_BUCKET_NAME=your_s3_bucket_name # for example, my-neon-app-s3-uploads

# Database Connection String
DATABASE_URL=your_database_connection_string

The following code snippet demonstrates this workflow:

JavaScript

import { serve } from '@hono/node-server';
import { Hono } from 'hono';
import { S3Client, PutObjectCommand } from '@aws-sdk/client-s3';
import { getSignedUrl } from '@aws-sdk/s3-request-presigner';
import { neon } from '@neondatabase/serverless';
import 'dotenv/config';
import { randomUUID } from 'crypto';

const S3_BUCKET = process.env.S3_BUCKET_NAME;
const AWS_REGION = process.env.AWS_REGION;
const s3 = new S3Client({
  region: AWS_REGION,
  credentials: {
    accessKeyId: process.env.AWS_ACCESS_KEY_ID,
    secretAccessKey: process.env.AWS_SECRET_ACCESS_KEY,
  },
});
const sql = neon(process.env.DATABASE_URL);
const app = new Hono();

// Replace this with your actual user authentication logic, by validating JWTs/Headers, etc.
const authMiddleware = async (c, next) => {
  c.set('userId', 'user_123');
  await next();
};

// 1. Generate Presigned URL for Upload
app.post('/presign-upload', authMiddleware, async (c) => {
  try {
    const { fileName, contentType } = await c.req.json();
    if (!fileName || !contentType) throw new Error('fileName and contentType required');

    const objectKey = `${randomUUID()}-${fileName}`;
    const publicFileUrl = `https://${S3_BUCKET}.s3.${AWS_REGION}.amazonaws.com/${objectKey}`;

    const command = new PutObjectCommand({
      Bucket: S3_BUCKET,
      Key: objectKey,
      ContentType: contentType,
    });
    const presignedUrl = await getSignedUrl(s3, command, { expiresIn: 300 });

    return c.json({ success: true, presignedUrl, objectKey, publicFileUrl });
  } catch (error) {
    console.error('Presign Error:', error.message);
    return c.json({ success: false, error: 'Failed to prepare upload' }, 500);
  }
});

// 2. Save Metadata after Client Upload Confirmation
app.post('/save-metadata', authMiddleware, async (c) => {
  try {
    const { objectKey, publicFileUrl } = await c.req.json();
    const userId = c.get('userId');
    if (!objectKey) throw new Error('objectKey required');

    await sql`
      INSERT INTO s3_files (object_key, file_url, user_id)
      VALUES (${objectKey}, ${publicFileUrl}, ${userId})
    `;
    console.log(`Metadata saved for S3 object: ${objectKey}`);
    return c.json({ success: true });
  } catch (error) {
    console.error('Metadata Save Error:', error.message);
    return c.json({ success: false, error: 'Failed to save metadata' }, 500);
  }
});

const port = 3000;
serve({ fetch: app.fetch, port }, (info) => {
  console.log(`Server running at http://localhost:${info.port}`);
});

Explanation

Setup: Initializes the Neon database client (sql), Hono (app), and the AWS S3 client (s3) configured with region and credentials.
Authentication: A placeholder authMiddleware is included. Crucially, this needs to be replaced with real authentication logic. It currently just sets a static userId for demonstration.
Upload endpoints:
- /presign-upload: Generates a temporary secure URL (presignedUrl) using @aws-sdk/s3-request-presigner that allows uploading a file directly to S3. It returns the URL, the generated objectKey, and the standard S3 public URL.
- /save-metadata: Called by the client after successful upload. Saves the objectKey, file_url, and userId into the s3_files table in Neon using @neondatabase/serverless.

We'll use Flask, boto3 (AWS SDK for Python), and psycopg2.

First, install the necessary dependencies:

Bash

pip install Flask boto3 psycopg2-binary python-dotenv

Create a .env file:

env

# AWS S3 Credentials & Config
AWS_ACCESS_KEY_ID=your_iam_user_access_key_id
AWS_SECRET_ACCESS_KEY=your_iam_user_secret_access_key
AWS_REGION=your_s3_bucket_region # for example, us-east-1
S3_BUCKET_NAME=your_s3_bucket_name # for example, my-neon-app-s3-uploads

# Database Connection String
DATABASE_URL=your_database_connection_string

The following code snippet demonstrates this workflow:

Python

import os
import uuid

import boto3
import psycopg2
from botocore.exceptions import ClientError
from dotenv import load_dotenv
from flask import Flask, jsonify, request

load_dotenv()

S3_BUCKET_NAME = os.getenv("S3_BUCKET_NAME")
AWS_REGION = os.getenv("AWS_REGION")
s3_client = boto3.client(
    service_name="s3",
    region_name=AWS_REGION,
    aws_access_key_id=os.getenv("AWS_ACCESS_KEY_ID"),
    aws_secret_access_key=os.getenv("AWS_SECRET_ACCESS_KEY"),
)

app = Flask(__name__)

# Use a global PostgreSQL connection instead of creating a new one for each request in production
def get_db_connection():
    return psycopg2.connect(os.getenv("DATABASE_URL"))

# Replace this with your actual user authentication logic
def get_authenticated_user_id(request):
    # Example: Validate Authorization header, session cookie, etc.
    return "user_123"  # Static ID for demonstration

# 1. Generate Presigned URL for Upload
@app.route("/presign-upload", methods=["POST"])
def presign_upload_route():
    try:
        user_id = get_authenticated_user_id(request)
        data = request.get_json()
        file_name = data.get("fileName")
        content_type = data.get("contentType")
        if not file_name or not content_type:
            raise ValueError("fileName and contentType required")

        object_key = f"{uuid.uuid4()}-{file_name}"
        public_file_url = (
            f"https://{S3_BUCKET_NAME}.s3.{AWS_REGION}.amazonaws.com/{object_key}"
        )

        presigned_url = s3_client.generate_presigned_url(
            "put_object",
            Params={
                "Bucket": S3_BUCKET_NAME,
                "Key": object_key,
                "ContentType": content_type,
            },
            ExpiresIn=300,
        )
        return jsonify(
            {
                "success": True,
                "presignedUrl": presigned_url,
                "objectKey": object_key,
                "publicFileUrl": public_file_url,
            }
        ), 200

    except (ClientError, ValueError) as e:
        print(f"Presign Error: {e}")
        return jsonify(
            {"success": False, "error": f"Failed to prepare upload: {e}"}
        ), 500
    except Exception as e:
        print(f"Unexpected Presign Error: {e}")
        return jsonify({"success": False, "error": "Server error"}), 500

# 2. Save Metadata after Client Upload Confirmation
@app.route("/save-metadata", methods=["POST"])
def save_metadata_route():
    conn = None
    cursor = None
    try:
        user_id = get_authenticated_user_id(request)
        data = request.get_json()
        object_key = data.get("objectKey")
        public_file_url = data.get("publicFileUrl")
        if not object_key:
            raise ValueError("objectKey required")

        conn = get_db_connection()
        cursor = conn.cursor()
        cursor.execute(
            """ INSERT INTO s3_files (object_key, file_url, user_id) VALUES (%s, %s, %s) """,
            (object_key, public_file_url, user_id),
        )
        conn.commit()
        print(f"Metadata saved for S3 object: {object_key}")
        return jsonify({"success": True}), 201
    except (psycopg2.Error, ValueError) as e:
        print(f"Metadata Save Error: {e}")
        return jsonify(
            {"success": False, "error": "Failed to save metadata"}
        ), 500
    except Exception as e:
        print(f"Unexpected Metadata Save Error: {e}")
        return jsonify({"success": False, "error": "Server error"}), 500
    finally:
        if cursor: cursor.close()
        if conn: conn.close()

if __name__ == "__main__":
    port = int(os.environ.get("PORT", 3000))
    app.run(host="0.0.0.0", port=port, debug=True)

Explanation

Setup: Initializes Flask, the PostgreSQL client (psycopg2), and the AWS S3 client (boto3) using environment variables for credentials and configuration.
Authentication: A placeholder get_authenticated_user_id function is included. Replace this with real authentication logic.
Upload endpoints:
- /presign-upload: Generates a temporary secure URL (presignedUrl) using boto3 that allows uploading a file directly to S3. It returns the URL, objectKey, and the standard public S3 URL.
- /save-metadata: Called by the client after successful upload. Saves the objectKey, file_url, and userId into the s3_files table in Neon using psycopg2.
In production, you should use a global PostgreSQL connection instead of creating a new one for each request. This is important for performance and resource management.

Testing the upload workflow
Testing the presigned URL flow involves multiple steps:
1. Get presigned URL: Send a POST request to your /presign-upload endpoint with a JSON body containing fileName and contentType. Using cURL:
  Bash
```
curl -X POST http://localhost:3000/presign-upload \
     -H "Content-Type: application/json" \
     -d '{"fileName": "test-s3.txt", "contentType": "text/plain"}'
```
  You should receive a JSON response with a presignedUrl, objectKey, and publicFileUrl:
  JSON
```
{
  "success": true,
  "presignedUrl": "https://<BUCKET_NAME>.s3.us-east-1.amazonaws.com/.....&x-id=PutObject",
  "objectKey": "<OBJECT_KEY>",
  "publicFileUrl": "https://<BUCKET_NAME>.s3.us-east-1.amazonaws.com/<OBJECT_KEY>"
}
```
  Note the presignedUrl, objectKey, and publicFileUrl from the response. You will use these in the next steps.
2. Upload file to S3: Use the received presignedUrl to upload the actual file using an HTTP PUT request. Using cURL:
  Bash
```
curl -X PUT "<PRESIGNED_URL>" \
     --upload-file /path/to/your/test-s3.txt \
     -H "Content-Type: text/plain"
```
  A successful upload typically returns HTTP 200 OK with no body.
3. Save metadata: Send a POST request to your /save-metadata endpoint with the objectKey and publicFileUrl obtained in step 1. Using cURL:
  Bash
```
curl -X POST http://localhost:3000/save-metadata \
     -H "Content-Type: application/json" \
     -d '{"objectKey": "<OBJECT_KEY>", "publicFileUrl": "<PUBLIC_URL>"}'
```
  You should receive a JSON response indicating success:
  JSON
```
{ "success": true }
```
Expected outcome:
- The file appears in your S3 bucket (check the AWS Console).
- A new row appears in your s3_files table in Neon containing the object_key and file_url.
You can now integrate API calls to these endpoints from various parts of your application (for example, web clients using JavaScript's fetch API, mobile apps, backend services) to handle file uploads.
Accessing file metadata and files
Storing metadata in the database allows your application to easily retrieve references to the files hosted on S3.
Query the s3_files table from your application's backend when needed.
Example SQL query:
Retrieve files for user 'user_123':
SQL
```
SELECT
    id,
    object_key,     -- Key (path/filename) in S3
    file_url,       -- Publicly accessible S3 URL
    user_id,        -- User associated with the file
    upload_timestamp
FROM
    s3_files
WHERE
    user_id = 'user_123'; -- Use actual authenticated user ID
```
Using the data:
- The query returns metadata stored in the database.
- The file_url column contains the direct link to access the file via S3.
- Use this file_url in your application (for example, <img> tags, download links)For private S3 buckets, store only the object_key and generate presigned read URLs on demand using a similar backend process.
This pattern effectively separates file storage and delivery concerns (handled by S3) from structured metadata management (handled by Postgres), leveraging the strengths of both services.

Resources

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