diff --git a/README.md b/README.md
index c001a22..bb8f79e 100644
--- a/README.md
+++ b/README.md
@@ -418,9 +418,9 @@ If provided, cacache will memoize the given cache insertion in memory, bypassing
 any filesystem checks for that key or digest in future cache fetches. Nothing
 will be written to the in-memory cache unless this option is explicitly truthy.
 
-There is no facility for limiting memory usage short of
-[`cacache.clearMemoized()`](#clear-memoized), so be mindful of the sort of data
-you ask to get memoized!
+If `opts.memoize` is an object or a `Map`-like (that is, an object with `get`
+and `set` methods), it will be written to instead of the global memoization
+cache.
 
 Reading from existing memoized data can be forced by explicitly passing
 `memoize: false` to the reader functions, but their default will be to read from
diff --git a/get.js b/get.js
index 19ed4d1..58adb8e 100644
--- a/get.js
+++ b/get.js
@@ -19,8 +19,8 @@ function getData (byDigest, cache, key, opts) {
   opts = opts || {}
   const memoized = (
     byDigest
-    ? memo.get.byDigest(cache, key)
-    : memo.get(cache, key)
+    ? memo.get.byDigest(cache, key, opts)
+    : memo.get(cache, key, opts)
   )
   if (memoized && opts.memoize !== false) {
     return BB.resolve(byDigest ? memoized : {
@@ -46,9 +46,9 @@ function getData (byDigest, cache, key, opts) {
       integrity: entry.integrity
     }).then(res => {
       if (opts.memoize && byDigest) {
-        memo.put.byDigest(cache, key, res)
+        memo.put.byDigest(cache, key, res, opts)
       } else if (opts.memoize) {
-        memo.put(cache, entry, res.data)
+        memo.put(cache, entry, res.data, opts)
       }
       return res
     })
@@ -59,7 +59,7 @@ module.exports.stream = getStream
 function getStream (cache, key, opts) {
   opts = opts || {}
   let stream = through()
-  const memoized = memo.get(cache, key)
+  const memoized = memo.get(cache, key, opts)
   if (memoized && opts.memoize !== false) {
     stream.on('newListener', function (ev, cb) {
       ev === 'metadata' && cb(memoized.entry.metadata)
@@ -84,7 +84,7 @@ function getStream (cache, key, opts) {
         memoLength += c.length
         cb(null, c, en)
       }, cb => {
-        memoData && memo.put(cache, entry, Buffer.concat(memoData, memoLength))
+        memoData && memo.put(cache, entry, Buffer.concat(memoData, memoLength), opts)
         cb()
       })
     } else {
@@ -111,7 +111,7 @@ function getStream (cache, key, opts) {
 module.exports.stream.byDigest = getStreamDigest
 function getStreamDigest (cache, integrity, opts) {
   opts = opts || {}
-  const memoized = memo.get.byDigest(cache, integrity)
+  const memoized = memo.get.byDigest(cache, integrity, opts)
   if (memoized && opts.memoize !== false) {
     const stream = through()
     stream.write(memoized, () => stream.end())
@@ -129,7 +129,8 @@ function getStreamDigest (cache, integrity, opts) {
         memoData && memo.put.byDigest(
           cache,
           integrity,
-          Buffer.concat(memoData, memoLength)
+          Buffer.concat(memoData, memoLength),
+          opts
         )
         cb()
       })
@@ -142,7 +143,7 @@ function getStreamDigest (cache, integrity, opts) {
 module.exports.info = info
 function info (cache, key, opts) {
   opts = opts || {}
-  const memoized = memo.get(cache, key)
+  const memoized = memo.get(cache, key, opts)
   if (memoized && opts.memoize !== false) {
     return BB.resolve(memoized.entry)
   } else {
diff --git a/lib/memoization.js b/lib/memoization.js
index abbab9b..92179c7 100644
--- a/lib/memoization.js
+++ b/lib/memoization.js
@@ -28,22 +28,42 @@ function clearMemoized () {
 }
 
 module.exports.put = put
-function put (cache, entry, data) {
-  MEMOIZED.set(`key:${cache}:${entry.key}`, { entry, data })
-  putDigest(cache, entry.integrity, data)
+function put (cache, entry, data, opts) {
+  pickMem(opts).set(`key:${cache}:${entry.key}`, { entry, data })
+  putDigest(cache, entry.integrity, data, opts)
 }
 
 module.exports.put.byDigest = putDigest
-function putDigest (cache, integrity, data) {
-  MEMOIZED.set(`digest:${cache}:${integrity}`, data)
+function putDigest (cache, integrity, data, opts) {
+  pickMem(opts).set(`digest:${cache}:${integrity}`, data)
 }
 
 module.exports.get = get
-function get (cache, key) {
-  return MEMOIZED.get(`key:${cache}:${key}`)
+function get (cache, key, opts) {
+  return pickMem(opts).get(`key:${cache}:${key}`)
 }
 
 module.exports.get.byDigest = getDigest
-function getDigest (cache, integrity) {
-  return MEMOIZED.get(`digest:${cache}:${integrity}`)
+function getDigest (cache, integrity, opts) {
+  return pickMem(opts).get(`digest:${cache}:${integrity}`)
+}
+
+class ObjProxy {
+  constructor (obj) {
+    this.obj = obj
+  }
+  get (key) { return this.obj[key] }
+  set (key, val) { this.obj[key] = val }
+}
+
+function pickMem (opts) {
+  if (!opts || !opts.memoize) {
+    return MEMOIZED
+  } else if (opts.memoize.get && opts.memoize.set) {
+    return opts.memoize
+  } else if (typeof opts.memoize === 'object') {
+    return new ObjProxy(opts.memoize)
+  } else {
+    return MEMOIZED
+  }
 }
diff --git a/put.js b/put.js
index 5f525d0..fe1293e 100644
--- a/put.js
+++ b/put.js
@@ -13,7 +13,7 @@ function putData (cache, key, data, opts) {
     opts.size = res.size
     return index.insert(cache, key, res.integrity, opts).then(entry => {
       if (opts.memoize) {
-        memo.put(cache, entry, data)
+        memo.put(cache, entry, data, opts)
       }
       return res.integrity
     })
@@ -49,7 +49,7 @@ function putStream (cache, key, opts) {
       opts.size = size
       index.insert(cache, key, integrity, opts).then(entry => {
         if (opts.memoize) {
-          memo.put(cache, entry, Buffer.concat(memoData, memoTotal))
+          memo.put(cache, entry, Buffer.concat(memoData, memoTotal), opts)
         }
         stream.emit('integrity', integrity)
         cb()
diff --git a/test/memoization.js b/test/memoization.js
index e6ef1f8..1a6c8f6 100644
--- a/test/memoization.js
+++ b/test/memoization.js
@@ -66,3 +66,96 @@ test('can clear out the memoization cache', t => {
   )
   t.done()
 })
+
+test('accepts optional injected cache', t => {
+  memo.clearMemoized()
+  const MEMO = new Map()
+  memo.put(CACHE, ENTRY, DATA, {memoize: MEMO})
+  t.deepEqual(
+    memo.get(CACHE, ENTRY.key),
+    null,
+    'entry not in global memo cache'
+  )
+  t.deepEqual(
+    memo.get(CACHE, ENTRY.key, {memoize: MEMO}),
+    {entry: ENTRY, data: DATA},
+    'entry fetched from injected memoizer'
+  )
+  t.deepEqual(
+    memo.get.byDigest(CACHE, ENTRY.integrity, {memoize: MEMO}),
+    DATA,
+    'content entry fetched from injected memoizer'
+  )
+  t.deepEqual(
+    MEMO.get(`key:${CACHE}:${ENTRY.key}`),
+    {entry: ENTRY, data: DATA},
+    'entry is in the injected memoizer'
+  )
+  t.deepEqual(
+    MEMO.get(`digest:${CACHE}:${ENTRY.integrity}`),
+    DATA,
+    'content entry is in the injected memoizer'
+  )
+  MEMO.clear()
+  t.deepEqual(
+    memo.get(CACHE, ENTRY.key, {memoize: MEMO}),
+    null,
+    'tried to read from cleared memoizer'
+  )
+  t.deepEqual(
+    memo.get.byDigest(CACHE, ENTRY.integrity, {memoize: MEMO}),
+    null,
+    'tried to read by digest from cleared memoizer'
+  )
+  memo.put.byDigest(CACHE, ENTRY.integrity, DATA, {memoize: MEMO})
+  t.deepEqual(
+    MEMO.get(`digest:${CACHE}:${ENTRY.integrity}`),
+    DATA,
+    'content entry is in the injected memoizer'
+  )
+  const obj = {}
+  memo.put(CACHE, ENTRY, DATA, {memoize: obj})
+  t.deepEqual(
+    memo.get(CACHE, ENTRY.key, {memoize: obj}),
+    {entry: ENTRY, data: DATA},
+    'entry fetched from injected object memoizer'
+  )
+  t.deepEqual(
+    memo.get.byDigest(CACHE, ENTRY.integrity, {memoize: MEMO}),
+    DATA,
+    'content entry fetched from injected object memoizer'
+  )
+  memo.clearMemoized()
+  memo.put(CACHE, ENTRY, DATA, {memoize: 'foo'})
+  t.deepEqual(
+    memo.get(CACHE, ENTRY.key, {memoize: 'foo'}),
+    {entry: ENTRY, data: DATA},
+    'entry fetched from global memoization obj on non-obj option'
+  )
+  t.deepEqual(
+    memo.get(CACHE, ENTRY.key, {memoize: 'foo'}),
+    {entry: ENTRY, data: DATA},
+    'entry fetched from global memoization obj on non-obj option'
+  )
+  t.deepEqual(
+    memo.get.byDigest(CACHE, ENTRY.integrity, {memoize: 'foo'}),
+    DATA,
+    'content entry fetched global memoizer obj on non-obj option'
+  )
+  t.deepEqual(
+    memo.get.byDigest(CACHE, ENTRY.integrity, {memoize: 'foo'}),
+    DATA,
+    'content entry fetched global memoizer obj on non-obj option'
+  )
+  t.deepEqual(
+    memo.get.byDigest(CACHE, ENTRY.integrity, {memoize: false}),
+    DATA,
+    'content entry fetched global memoizer obj on non-obj option'
+  )
+  t.deepEqual(
+    memo.get.byDigest(CACHE, ENTRY.integrity, {memoize: false}),
+    DATA,
+    'content entry fetched global memoizer obj on non-obj option'
+  )
+  t.done()
+})