Pseudo-Memcached Protocol Server

Implement a simplified memcached-style TCP key-value server supporting line-based `get` / `set` commands with byte-count-framed values and a multi-key `get` bonus. Reddit's "Backend Coding" round, which recruiters flag as distinct from the usual algorithmic coding screen. Requirements Implement a server for a simplified, memcached-like in-memory key-value store. Clients connect over TCP and issue line-based, ASCII, case-sensitive commands (each line terminated by \n). Valid keys match [A-Za-z0-9_-]; values may be arbitrary bytes. Anything in the standard library is allowed. Commands to support: get key_name — look up the key and return its value in the form: VALUE key_name byte_count <raw data of byte_count bytes> END END\n terminates the response. If the key does not exist, send no VALUE line or data section — just END\n. set key_name byte_count — the client then sends byte_count bytes of data followed by a newline. Store the data under the key and respond with STORED\n. Bonus — multi-key get: extend get to accept multiple keys (get key_a key_b ...) and return all their values in one response (a VALUE/data block per existing key, then a single END). This is Reddit's "Backend Coding" round, which recruiters flag as different from the usual algorithmic coding screen — the focus is correct protocol handling and byte-accurate framing, not algorithmic complexity. Examples >>> get does_not_exist\n <<< END\n Notes The protocol is byte-count framed, not delimiter-framed: after a set, read exactly byte_count bytes (values may themselves contain newlines), then consume the trailing newline. Reading line-by-line breaks on binary or multi-line values. get on a missing key returns only END — no error, no VALUE line. Keys are validated against [A-Za-z0-9_-]; commands are case-sensitive. A correct solution typically wires a TCP socket server to a dict-backed store plus a small command parser; the standard library is explicitly allowed, so no third-party networking dependency is needed. Preparation Write a minimal TCP server in your target language from memory (socket / socketserver in Python), then layer command parsing on top. Drill byte-exact reads: read byte_count bytes precisely rather than readline, and reproduce the VALUE key n\n<data>\nEND\n framing exactly. Implement the multi-key get bonus so the response concatenates one block per existing key before a single END.