MEMORY USAGE

Estimates the memory usage of a key.

Browse all commands · Upstream source documentation

Reference field	Value
Canonical name	MEMORY USAGE
Catalog group	Server commands
Upstream since	4.0.0 — upstream Redis/module version, not an ffkv release
Pinned catalog	Redis 8.10.0

Syntax

MEMORY USAGE key [SAMPLES count]

ffkv behavior and limits

Server introspection describes ffkv, not a Redis process. MEMORY reports owned-allocation estimates, not jemalloc accounting. Administrative changes can affect all clients or persistent data; consult the scenario and operations guide before using destructive forms.

Source: README.md:393–395, 601–642; tests/bdd/features/server.feature; tests/bdd/features/catalog.feature.

All requests share the 8 MiB framing/1,024-argument ingress limit; normal RESP replies have 64 MiB wire/logical budgets with bounded nesting/value counts. Management and Lua origins impose smaller budgets. These are not a process RSS cap. Catalog inclusion is not exhaustive option or wire-format parity. See limits and compatibility.

Upstream metadata

The following fields come from the pinned Redis metadata, not measured ffkv performance or an assertion that ffkv enforces every upstream flag. Running COMMAND INFO/COMMAND DOCS describe the current engine.

Upstream Redis complexity: O(N) where N is the number of samples.

Upstream arity: -3 (includes the command name; a negative number is a minimum).

Command flags: READONLY.

Argument structure

Argument	Type	Constraints / metadata
key	key	key_spec_index: 0
count	integer	optional; token: SAMPLES

Key specifications

Upstream key discovery descriptors (indexes are relative to the full command vector):

[
  {
    "flags": [
      "RO"
    ],
    "begin_search": {
      "index": {
        "pos": 2
      }
    },
    "find_keys": {
      "range": {
        "lastkey": 0,
        "step": 1,
        "limit": 0
      }
    }
  }
]

Additional pinned upstream metadata

{
  "group": "server",
  "since": "4.0.0"
}

Metadata source · Local snapshot: src/command_metadata.json, key memory|usage.

BDD coverage and source examples

These are source observations, not a test run performed by this documentation build. A tag identifies scenario intent; an extracted vector identifies a command invocation, which may intentionally produce an error. Scenarios may require setup, multiple connections, persistence, cluster nodes or native-module fixtures.

• Memory diagnostics account for live data without inventing allocator internals — tests/bdd/features/server.feature:313; command tag and invocation observed.
• Transactional configuration publishes effective values and observations do not repause engines — tests/bdd/features/transactions_runtime.feature:5; command tag and invocation observed.
• Memory usage inside EXEC observes the database selected by a preceding queued command — tests/bdd/features/transactions_runtime.feature:169; command tag and invocation observed.

Extracted command vectors

The following JSON arrays are the test harness’s argument vectors, not shell commands. Numeric arguments are converted by the harness; objects of the form {"base64":"…"} represent decoded binary bytes, not a literal JSON command argument. Preserve scenario setup and connection ordering. See the CLI guide for shell quoting and binary stdin. No reply is invented or inferred.

Memory diagnostics account for live data without inventing allocator internals — tests/bdd/features/server.feature:363 (I execute:)

[
  "MEMORY",
  "USAGE",
  "memory:item"
]

Next source assertion: the reply is null

Transactional configuration publishes effective values and observations do not repause engines — tests/bdd/features/transactions_runtime.feature:32 (client “admin” executes:)

[
  "MEMORY",
  "USAGE",
  "missing:transaction:key",
  "SAMPLES",
  "0"
]

Next source assertion: the reply equals:

"QUEUED"

Memory usage inside EXEC observes the database selected by a preceding queued command — tests/bdd/features/transactions_runtime.feature:171 (the following commands succeed:)

[
  "MEMORY",
  "USAGE",
  "transaction:database"
]