Coverage matrix

This is the canonical map of logical operations to wire commands. Each row describes one thing a client can ask the server to do; each column shows how that operation is expressed in a given protocol.

Cell value	Meaning
name	Concrete command, opcode, or meta form (clickable)
–	Not applicable to this protocol
stub	Recognised but returns synthetic output (no real backing)
no	Not implemented; the command is rejected or ignored

Operation	memcached text	memcached binary	memcached meta	Redis RESP2
Store value unconditionally	set	0x01 SET / 0x11 SETQ	ms M=S	SET
Store only if absent	add	0x02 ADD / 0x12 ADDQ	ms M=E	SET NX
Store only if present	replace	0x03 REPLACE / 0x13 REPLACEQ	ms M=R	SET XX
Append to existing value	append	0x0e APPEND / 0x19 APPENDQ	ms M=A	no
Prepend to existing value	prepend	0x0f PREPEND / 0x1a PREPENDQ	ms M=P	no
Compare-and-swap	cas	via CAS field in header	ms C(token)	–
Fetch by key	get	0x00 GET / 0x09 GETQ / 0x0c GETK / 0x0d GETKQ	mg v	GET
Fetch with CAS	gets	implicit (CAS in header)	mg c v	–
Fetch and refresh TTL	gat / gats	0x1d GAT / 0x1e GATQ / 0x23 GATK / 0x24 GATKQ	mg v T(token)	no
Refresh TTL without reading value	touch	0x1c TOUCH	mg T(token)	no
Increment numeric value	incr	0x05 INCREMENT / 0x15 INCREMENTQ	ma M=I	no
Decrement numeric value	decr	0x06 DECREMENT / 0x16 DECREMENTQ	ma M=D	no
Auto-vivify on miss	–	0x05/0x06 with exptime!=0xFFFFFFFF	mg N(token) / ma N J	–
Delete key	delete	0x04 DELETE / 0x14 DELETEQ	md	DEL / UNLINK
Mark stale (recache coordination)	–	–	md I / ms I	–
Drop all entries	flush_all	0x08 FLUSH / 0x18 FLUSHQ	–	FLUSHDB / FLUSHALL
Check key existence	implicit via get	implicit via 0x00	mg h	EXISTS
Server version	version	0x0b VERSION	–	inside INFO
Server stats	stats + sub-commands	0x10 STAT	per-entry via me	INFO
Set memory limit at runtime	cache_memlimit	–	–	–
Verbosity dial	verbosity (no-op)	0x1b VERBOSITY (no-op)	–	–
Close connection	quit	0x07 QUIT / 0x17 QUITQ	–	QUIT
Heartbeat	–	0x0a NOOP	mn	PING
Pipeline sync barrier	–	–	mn	–
Slab rebalance	stub (slabs)	–	–	–
LRU tuning	stub (lru)	–	–	–
LRU crawler control	stub (lru_crawler)	–	–	–
Event watch streaming	no	–	–	–
Authentication	–	SASL rejected	–	AUTH rejected
Echo	–	–	–	ECHO
Server handshake	–	–	–	HELLO
Command introspection	–	–	–	COMMAND (empty array)
Select database	–	–	–	SELECT accepted (no-op, single keyspace)
Client connection setup	–	–	–	CLIENT stub
Runtime config probe	–	–	–	CONFIG stub
Pub / sub	–	–	–	no
Scripting (EVAL)	–	–	–	no
Streams / sorted sets / hashes	–	–	–	no

Reading the matrix

• A row marked no in every column is an operation fastcached does not support in any protocol.
• A cell marked – means the protocol doesn't have a way to express the operation, so the absence is not a fastcached limitation.
• "stub" cells return well-shaped responses (OK) so capability-probing clients don't error out, but no underlying state is changed. See the linked command page for each stub's exact behavior.