What is the difference between symmetric and asymmetric encryption, and when do you use each?

Symmetric encryption uses one shared key for both encryption and decryption (AES-256, 3DES), while asymmetric uses a public-private key pair (RSA, ECC). Symmetric is 1000x faster, ideal for bulk data encryption—TLS uses AES after handshake, IPsec tunnels, disk encryption. Asymmetric handles key exchange and digital signatures—TLS handshake, SSH authentication, certificate signing. Real-world: Razorpay uses RSA 2048 for API authentication but AES-256-GCM for payment data at rest. Interview tip: Bangalore SOC roles expect you to explain why HTTPS combines both—RSA establishes session, AES encrypts traffic.