If you define a VARCHAR(255) column with utf8mb4 encoding, how does MySQL calculate the maximum possible storage size for that column, and how does it differ from CHAR(255)?

CHAR is fixed-length and always allocates full size.

Each character may need up to 4 bytes in utf8mb4.

Total storage = 255 × 4 = 1020 bytes (always reserved).

CHAR adds 1 byte for padding metadata internally.

CHAR wastes more space but is faster for fixed-length lookups.

VARCHAR stores variable-length data with 1–2 bytes overhead; CHAR always stores fixed-length.

VARCHAR(255) max size = 1022 bytes; CHAR(255) always uses 1020 bytes.

CHAR is less space-efficient with utf8mb4 because every row reserves the full 255 characters × 4 bytes.

VARCHAR is preferred for variable-length text; CHAR is ideal for fixed-size data like hashes or codes.