Start by clarifying requirements and constraints, then design a binary format with a fixed header and type-tagged, length-prefixed values, ensuring O(n) encode/decode. Implement the encoder/decoder, and finally compare tradeoffs with JSON and MessagePack, highlighting performance, size, and schema evolution.
Pro tip: Mention that you would use a recursive descent parser for nested maps and include a checksum like CRC32 for integrity, but note that checksums add overhead and may be optional for trusted environments.
Ask about expected data sizes, performance needs, schema evolution, and whether the format must be human-readable. Confirm that O(n) time is required and discuss memory constraints.
Define a fixed header with magic bytes, version, and flags. Choose big-endian for network order. Assign type tags for each value type and use length prefixes for strings and maps.
Write recursive functions that traverse the map, writing type tags and values. For decode, read the header, validate magic and version, then recursively reconstruct the map. Ensure O(n) by processing each byte once.
Compute a checksum (e.g., CRC32) over the payload and include it in the header. On decode, verify the checksum and handle malformed data gracefully.
Compare with JSON (human-readable, larger, slower) and MessagePack (compact, fast, but less schema flexibility). Highlight when to choose each based on performance, size, and interoperability.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.