Q. How to deal with encoding (binary, base64, hex) when encrypting strings?
A: Data encryption yields binary output (buffers). You’ll often convert them to base64 or hex before sending through JSON or URLs. On decryption, convert back to Buffer and decrypt. Be consistent between encryption and decryption steps.
Q. How do I handle initialization vectors (IV) and salts correctly?
A: Use a unique, random IV per encryption (but IVs need not be secret, just unpredictable). Use a salt when deriving keys from passwords (e.g. with PBKDF2). Store the IV (and salt) alongside the ciphertext (e.g. prefix it). Use authenticated encryption modes (e.g. AES-GCM) so you can verify integrity and detect tampering.
Q. Symmetric vs asymmetric encryption — when to use which?
A: Symmetric (same key for encrypt/decrypt): faster; good for encrypting large payloads where both parties share a secret key (e.g., AES). Asymmetric (public/private key): used for key exchange, digital signatures, or when parties don’t share a secret. Performance is slower, so often used only to encrypt small data (e.g. symmetric key). A common pattern: generate […]
Q. Which crypto library should I use in Node.js?
A: You can use Node.js’s built-in crypto module (which supports many primitives: symmetric, asymmetric, hashing, HMAC) or use higher-level wrappers (e.g. crypto-js, node-forge). For simplicity and security, the built-in crypto is preferred because it’s maintained and optimized.
Q. How to ensure integrity and security of the uploaded file?
A: Use checksums like MD5 or SHA-256 per chunk or entire file, validate on the backend or via S3’s ETag. Use HTTPS to transmit. Restrict presigned URL permissions (e.g. only PUT, limited expiry). Optionally encrypt data at rest (S3 SSE) or client-side encryption before uploading. After upload, verify file metadata (size, type) and reject unexpected […]
Q. Are there size or time limits I should worry about?
A: Yes — AWS S3 has multipart upload limits (minimum part size ~5 MB, maximum 10,000 parts, total file size up to 5 TB). Also, HTTP timeouts, network interruptions, or browser limits might cause failures. So chunking and retry logic are important. Moreover, set appropriate Content-Length and Content-MD5 headers if you use them.
Q. How to resume or retry failed chunk uploads?
A: With S3 multipart upload, each chunk (part) has an ETag; if a part fails, you can retry that part. Track which parts succeeded vs failed (persist state). Use the S3 uploadId and part numbers. Implement logic in frontend to resume from failed chunks rather than re-upload all.
Q. Should I upload directly from React (client) to S3 or route via NestJS?
A: A common pattern is presigned URLs — the backend (NestJS) generates a presigned upload URL from S3 and returns it to React; React then uploads the file chunks directly to S3. This reduces load on your server and bandwidth. The backend can still verify file metadata and sign only authorized uploads.
Q. How do we avoid memory overload when uploading huge files?
A: Stream the upload instead of reading the full file into memory. Use streaming (e.g. createReadStream) and use multipart upload in S3 for large files to upload chunks. On the backend, use libraries (e.g. aws-sdk / @aws-sdk/client-s3) that support multipart upload. Also limit file size and concurrency, validate chunk sizes, and pipe data rather than […]
Q. How to manage connection pooling and concurrency?
A: Use a pool (e.g. Diesel + r2d2) to maintain multiple PostgreSQL connections. Configure max pool size based on expected load and DB resources. In Rocket, request guards can provide pooled connection references to handlers, ensuring reuse. Avoid opening a new connection per request. Also watch out for blocking DB operations — consider running long […]