diff --git a/server/modules/filter/cache/storage/storage_inmemory/CMakeLists.txt b/server/modules/filter/cache/storage/storage_inmemory/CMakeLists.txt
new file mode 100644
index 000000000..93a39ea58
--- /dev/null
+++ b/server/modules/filter/cache/storage/storage_inmemory/CMakeLists.txt
@@ -0,0 +1,10 @@
+add_library(storage_inmemory SHARED
+    inmemorystorage.cc
+    inmemorystoragest.cc
+    inmemorystoragemt.cc
+    storage_inmemory.cc
+    )
+target_link_libraries(storage_inmemory cache maxscale-common)
+set_target_properties(storage_inmemory PROPERTIES VERSION "1.0.0")
+set_target_properties(storage_inmemory PROPERTIES LINK_FLAGS -Wl,-z,defs)
+install_module(storage_inmemory experimental)
diff --git a/server/modules/filter/cache/storage/storage_inmemory/inmemorystorage.cc b/server/modules/filter/cache/storage/storage_inmemory/inmemorystorage.cc
new file mode 100644
index 000000000..874c68f2b
--- /dev/null
+++ b/server/modules/filter/cache/storage/storage_inmemory/inmemorystorage.cc
@@ -0,0 +1,195 @@
+/*
+ * Copyright (c) 2016 MariaDB Corporation Ab
+ *
+ * Use of this software is governed by the Business Source License included
+ * in the LICENSE.TXT file and at www.mariadb.com/bsl.
+ *
+ * Change Date: 2019-07-01
+ *
+ * On the date above, in accordance with the Business Source License, use
+ * of this software will be governed by version 2 or later of the General
+ * Public License.
+ */
+
+#define MXS_MODULE_NAME "storage_inmemory"
+#include "inmemorystorage.h"
+#include <openssl/sha.h>
+#include <algorithm>
+#include <set>
+#include <maxscale/alloc.h>
+#include <maxscale/modutil.h>
+#include <maxscale/query_classifier.h>
+
+using std::set;
+using std::string;
+
+
+namespace
+{
+
+const size_t INMEMORY_KEY_LENGTH = 2 * SHA512_DIGEST_LENGTH;
+
+#if INMEMORY_KEY_LENGTH > CACHE_KEY_MAXLEN
+#error storage_inmemory key is too long.
+#endif
+
+}
+
+InMemoryStorage::InMemoryStorage(const string& name,
+                                 uint32_t ttl)
+    : name_(name)
+    , ttl_(ttl)
+{
+}
+
+InMemoryStorage::~InMemoryStorage()
+{
+}
+
+cache_result_t InMemoryStorage::get_key(const char* zdefault_db, const GWBUF* pquery, CACHE_KEY* pkey)
+{
+    ss_dassert(GWBUF_IS_CONTIGUOUS(pquery));
+
+    int n;
+    bool fullnames = true;
+    char** pztables = qc_get_table_names(const_cast<GWBUF*>(pquery), &n, fullnames);
+
+    set<string> dbs; // Elements in set are sorted.
+
+    for (int i = 0; i < n; ++i)
+    {
+        char *ztable = pztables[i];
+        char *zdot = strchr(ztable, '.');
+
+        if (zdot)
+        {
+            *zdot = 0;
+            dbs.insert(ztable);
+        }
+        else if (zdefault_db)
+        {
+            // If zdefault_db is NULL, then there will be a table for which we
+            // do not know the database. However, that will fail in the server,
+            // so nothing will be stored.
+            dbs.insert(zdefault_db);
+        }
+        MXS_FREE(ztable);
+    }
+    MXS_FREE(pztables);
+
+    // dbs now contain each accessed database in sorted order. Now copy them to a single string.
+    string tag;
+    for (set<string>::const_iterator i = dbs.begin(); i != dbs.end(); ++i)
+    {
+        tag.append(*i);
+    }
+
+    memset(pkey->data, 0, CACHE_KEY_MAXLEN);
+
+    const unsigned char* pdata;
+
+    // We store the databases in the first half of the key. That will ensure that
+    // identical queries targeting different default databases will not clash.
+    // This will also mean that entries related to the same databases will
+    // be placed near each other.
+    pdata = reinterpret_cast<const unsigned char*>(tag.data());
+    SHA512(pdata, tag.length(), reinterpret_cast<unsigned char*>(pkey->data));
+
+    char *psql;
+    int length;
+
+    modutil_extract_SQL(const_cast<GWBUF*>(pquery), &psql, &length);
+
+    // Then we store the query itself in the second half of the key.
+    pdata = reinterpret_cast<const unsigned char*>(psql);
+    SHA512(pdata, length, reinterpret_cast<unsigned char*>(pkey->data) + SHA512_DIGEST_LENGTH);
+
+    return CACHE_RESULT_OK;
+}
+
+cache_result_t InMemoryStorage::do_get_value(const CACHE_KEY& key, uint32_t flags, GWBUF** ppresult)
+{
+    cache_result_t result = CACHE_RESULT_NOT_FOUND;
+
+    Entries::iterator i = entries_.find(key);
+
+    if (i != entries_.end())
+    {
+        Entry& entry = i->second;
+
+        uint32_t now = time(NULL);
+
+        bool is_stale = (now - entry.time > ttl_);
+
+        if (!is_stale || ((flags & CACHE_FLAGS_INCLUDE_STALE) != 0))
+        {
+            size_t length = entry.value.size();
+
+            *ppresult = gwbuf_alloc(length);
+
+            if (*ppresult)
+            {
+                memcpy(GWBUF_DATA(*ppresult), entry.value.data(), length);
+
+                if (is_stale)
+                {
+                    result = CACHE_RESULT_STALE;
+                }
+                else
+                {
+                    result = CACHE_RESULT_OK;
+                }
+            }
+        }
+        else
+        {
+            MXS_NOTICE("Cache item is stale, not using.");
+            result = CACHE_RESULT_NOT_FOUND;
+        }
+    }
+    else
+    {
+        result = CACHE_RESULT_NOT_FOUND;
+    }
+
+    return result;
+}
+
+cache_result_t InMemoryStorage::do_put_value(const CACHE_KEY& key, const GWBUF* pvalue)
+{
+    ss_dassert(GWBUF_IS_CONTIGUOUS(pvalue));
+
+    const uint8_t* pdata = GWBUF_DATA(pvalue);
+    size_t size = GWBUF_LENGTH(pvalue);
+
+    Entry& entry = entries_[key];
+
+    if (size < entry.value.capacity())
+    {
+        // If the needed value is less than what is currently stored,
+        // we shrink the buffer so as not to waste space.
+        Value value(size);
+        entry.value.swap(value);
+    }
+    else
+    {
+        entry.value.resize(size);
+    }
+
+    copy(GWBUF_DATA(pvalue), GWBUF_DATA(pvalue) + size, entry.value.begin());
+    entry.time = time(NULL);
+
+    return CACHE_RESULT_OK;
+}
+
+cache_result_t InMemoryStorage::do_del_value(const CACHE_KEY& key)
+{
+    Entries::iterator i = entries_.find(key);
+
+    if (i != entries_.end())
+    {
+        entries_.erase(i);
+    }
+
+    return i != entries_.end() ? CACHE_RESULT_OK : CACHE_RESULT_NOT_FOUND;
+}
diff --git a/server/modules/filter/cache/storage/storage_inmemory/inmemorystorage.h b/server/modules/filter/cache/storage/storage_inmemory/inmemorystorage.h
new file mode 100644
index 000000000..d5bfeb610
--- /dev/null
+++ b/server/modules/filter/cache/storage/storage_inmemory/inmemorystorage.h
@@ -0,0 +1,62 @@
+#pragma once
+/*
+ * Copyright (c) 2016 MariaDB Corporation Ab
+ *
+ * Use of this software is governed by the Business Source License included
+ * in the LICENSE.TXT file and at www.mariadb.com/bsl.
+ *
+ * Change Date: 2019-07-01
+ *
+ * On the date above, in accordance with the Business Source License, use
+ * of this software will be governed by version 2 or later of the General
+ * Public License.
+ */
+
+#include <maxscale/cdefs.h>
+#include <memory>
+#include <string>
+#include <vector>
+#include <tr1/unordered_map>
+#include "../../cachefilter.h"
+
+class InMemoryStorage
+{
+public:
+    virtual ~InMemoryStorage();
+
+    cache_result_t get_key(const char* zdefault_db, const GWBUF* pquery, CACHE_KEY* pkey);
+
+    virtual cache_result_t get_value(const CACHE_KEY& key, uint32_t flags, GWBUF** ppresult) = 0;
+    virtual cache_result_t put_value(const CACHE_KEY& key, const GWBUF* pvalue) = 0;
+    virtual cache_result_t del_value(const CACHE_KEY& key) = 0;
+
+protected:
+    InMemoryStorage(const std::string& name, uint32_t ttl);
+
+    cache_result_t do_get_value(const CACHE_KEY& key, uint32_t flags, GWBUF** ppresult);
+    cache_result_t do_put_value(const CACHE_KEY& key, const GWBUF* pvalue);
+    cache_result_t do_del_value(const CACHE_KEY& key);
+
+private:
+    InMemoryStorage(const InMemoryStorage&);
+    InMemoryStorage& operator = (const InMemoryStorage&);
+
+private:
+    typedef std::vector<uint8_t> Value;
+
+    struct Entry
+    {
+        Entry()
+        : time(0)
+        {}
+
+        uint32_t time;
+        Value    value;
+    };
+
+    typedef std::tr1::unordered_map<CACHE_KEY, Entry> Entries;
+
+    std::string name_;
+    uint32_t    ttl_;
+    Entries     entries_;
+};
diff --git a/server/modules/filter/cache/storage/storage_inmemory/inmemorystoragemt.cc b/server/modules/filter/cache/storage/storage_inmemory/inmemorystoragemt.cc
new file mode 100644
index 000000000..b5497c27f
--- /dev/null
+++ b/server/modules/filter/cache/storage/storage_inmemory/inmemorystoragemt.cc
@@ -0,0 +1,60 @@
+/*
+ * Copyright (c) 2016 MariaDB Corporation Ab
+ *
+ * Use of this software is governed by the Business Source License included
+ * in the LICENSE.TXT file and at www.mariadb.com/bsl.
+ *
+ * Change Date: 2019-07-01
+ *
+ * On the date above, in accordance with the Business Source License, use
+ * of this software will be governed by version 2 or later of the General
+ * Public License.
+ */
+
+#define MXS_MODULE_NAME "storage_inmemory"
+#include "inmemorystoragemt.h"
+
+InMemoryStorageMT::InMemoryStorageMT(const std::string& name, uint32_t ttl)
+    : InMemoryStorage(name, ttl)
+{
+    spinlock_init(&lock_);
+}
+
+InMemoryStorageMT::~InMemoryStorageMT()
+{
+}
+
+// static
+InMemoryStorageMT* InMemoryStorageMT::create(const std::string& name,
+                                             uint32_t ttl,
+                                             int argc, char* argv[])
+{
+    return new InMemoryStorageMT(name, ttl);
+}
+
+cache_result_t InMemoryStorageMT::get_value(const CACHE_KEY& key, uint32_t flags, GWBUF** ppresult)
+{
+    spinlock_acquire(&lock_);
+    cache_result_t result = do_get_value(key, flags, ppresult);
+    spinlock_release(&lock_);
+
+    return result;
+}
+
+cache_result_t InMemoryStorageMT::put_value(const CACHE_KEY& key, const GWBUF* pvalue)
+{
+    spinlock_acquire(&lock_);
+    cache_result_t result = do_put_value(key, pvalue);
+    spinlock_release(&lock_);
+
+    return result;
+}
+
+cache_result_t InMemoryStorageMT::del_value(const CACHE_KEY& key)
+{
+    spinlock_acquire(&lock_);
+    cache_result_t result = do_del_value(key);
+    spinlock_release(&lock_);
+
+    return result;
+}
diff --git a/server/modules/filter/cache/storage/storage_inmemory/inmemorystoragemt.h b/server/modules/filter/cache/storage/storage_inmemory/inmemorystoragemt.h
new file mode 100644
index 000000000..0ad14d36e
--- /dev/null
+++ b/server/modules/filter/cache/storage/storage_inmemory/inmemorystoragemt.h
@@ -0,0 +1,39 @@
+#pragma once
+/*
+ * Copyright (c) 2016 MariaDB Corporation Ab
+ *
+ * Use of this software is governed by the Business Source License included
+ * in the LICENSE.TXT file and at www.mariadb.com/bsl.
+ *
+ * Change Date: 2019-07-01
+ *
+ * On the date above, in accordance with the Business Source License, use
+ * of this software will be governed by version 2 or later of the General
+ * Public License.
+ */
+
+#include <maxscale/cdefs.h>
+#include <maxscale/spinlock.h>
+#include "inmemorystorage.h"
+
+class InMemoryStorageMT : public InMemoryStorage
+{
+public:
+    ~InMemoryStorageMT();
+
+    static InMemoryStorageMT* create(const std::string& name, uint32_t ttl, int argc, char* argv[]);
+
+    cache_result_t get_value(const CACHE_KEY& key, uint32_t flags, GWBUF** ppresult);
+    cache_result_t put_value(const CACHE_KEY& key, const GWBUF* pvalue);
+    cache_result_t del_value(const CACHE_KEY& key);
+
+private:
+    InMemoryStorageMT(const std::string& name, uint32_t ttl);
+
+private:
+    InMemoryStorageMT(const InMemoryStorageMT&);
+    InMemoryStorageMT& operator = (const InMemoryStorageMT&);
+
+private:
+    SPINLOCK lock_;
+};
diff --git a/server/modules/filter/cache/storage/storage_inmemory/inmemorystoragest.cc b/server/modules/filter/cache/storage/storage_inmemory/inmemorystoragest.cc
new file mode 100644
index 000000000..0b81dd799
--- /dev/null
+++ b/server/modules/filter/cache/storage/storage_inmemory/inmemorystoragest.cc
@@ -0,0 +1,47 @@
+/*
+ * Copyright (c) 2016 MariaDB Corporation Ab
+ *
+ * Use of this software is governed by the Business Source License included
+ * in the LICENSE.TXT file and at www.mariadb.com/bsl.
+ *
+ * Change Date: 2019-07-01
+ *
+ * On the date above, in accordance with the Business Source License, use
+ * of this software will be governed by version 2 or later of the General
+ * Public License.
+ */
+
+#define MXS_MODULE_NAME "storage_inmemory"
+#include "inmemorystoragest.h"
+
+InMemoryStorageST::InMemoryStorageST(const std::string& name, uint32_t ttl)
+    : InMemoryStorage(name, ttl)
+{
+}
+
+InMemoryStorageST::~InMemoryStorageST()
+{
+}
+
+// static
+InMemoryStorageST* InMemoryStorageST::create(const std::string& name,
+                                             uint32_t ttl,
+                                             int argc, char* argv[])
+{
+    return new InMemoryStorageST(name, ttl);
+}
+
+cache_result_t InMemoryStorageST::get_value(const CACHE_KEY& key, uint32_t flags, GWBUF** ppresult)
+{
+    return do_get_value(key, flags, ppresult);
+}
+
+cache_result_t InMemoryStorageST::put_value(const CACHE_KEY& key, const GWBUF* pvalue)
+{
+    return do_put_value(key, pvalue);
+}
+
+cache_result_t InMemoryStorageST::del_value(const CACHE_KEY& key)
+{
+    return do_del_value(key);
+}
diff --git a/server/modules/filter/cache/storage/storage_inmemory/inmemorystoragest.h b/server/modules/filter/cache/storage/storage_inmemory/inmemorystoragest.h
new file mode 100644
index 000000000..4dac01c5d
--- /dev/null
+++ b/server/modules/filter/cache/storage/storage_inmemory/inmemorystoragest.h
@@ -0,0 +1,35 @@
+#pragma once
+/*
+ * Copyright (c) 2016 MariaDB Corporation Ab
+ *
+ * Use of this software is governed by the Business Source License included
+ * in the LICENSE.TXT file and at www.mariadb.com/bsl.
+ *
+ * Change Date: 2019-07-01
+ *
+ * On the date above, in accordance with the Business Source License, use
+ * of this software will be governed by version 2 or later of the General
+ * Public License.
+ */
+
+#include <maxscale/cdefs.h>
+#include "inmemorystorage.h"
+
+class InMemoryStorageST : public InMemoryStorage
+{
+public:
+    ~InMemoryStorageST();
+
+    static InMemoryStorageST* create(const std::string& name, uint32_t ttl, int argc, char* argv[]);
+
+    cache_result_t get_value(const CACHE_KEY& key, uint32_t flags, GWBUF** ppresult);
+    cache_result_t put_value(const CACHE_KEY& key, const GWBUF* pvalue);
+    cache_result_t del_value(const CACHE_KEY& key);
+
+private:
+    InMemoryStorageST(const std::string& name, uint32_t ttl);
+
+private:
+    InMemoryStorageST(const InMemoryStorageST&);
+    InMemoryStorageST& operator = (const InMemoryStorageST&);
+};
diff --git a/server/modules/filter/cache/storage/storage_inmemory/storage_inmemory.cc b/server/modules/filter/cache/storage/storage_inmemory/storage_inmemory.cc
new file mode 100644
index 000000000..b9cb1cd69
--- /dev/null
+++ b/server/modules/filter/cache/storage/storage_inmemory/storage_inmemory.cc
@@ -0,0 +1,233 @@
+/*
+ * Copyright (c) 2016 MariaDB Corporation Ab
+ *
+ * Use of this software is governed by the Business Source License included
+ * in the LICENSE.TXT file and at www.mariadb.com/bsl.
+ *
+ * Change Date: 2019-07-01
+ *
+ * On the date above, in accordance with the Business Source License, use
+ * of this software will be governed by version 2 or later of the General
+ * Public License.
+ */
+
+#define MXS_MODULE_NAME "storage_inmemory"
+#include <inttypes.h>
+#include "../../cache_storage_api.h"
+#include "inmemorystoragest.h"
+#include "inmemorystoragemt.h"
+
+namespace
+{
+
+bool initialize(uint32_t* pcapabilities)
+{
+    *pcapabilities = CACHE_STORAGE_CAP_ST;
+    *pcapabilities = CACHE_STORAGE_CAP_MT;
+
+    return true;
+}
+
+CACHE_STORAGE* createInstance(cache_thread_model_t model,
+                              const char* zname,
+                              uint32_t ttl,
+                              uint32_t max_count,
+                              uint64_t max_size,
+                              int argc, char* argv[])
+{
+    ss_dassert(zname);
+
+    CACHE_STORAGE* pStorage = 0;
+
+    if (max_count != 0)
+    {
+        MXS_WARNING("A maximum item count of %" PRIu32 " specified, although 'storage_inMemory' "
+                    "does not enforce such a limit.", max_count);
+    }
+
+    if (max_size != 0)
+    {
+        MXS_WARNING("A maximum size of %" PRIu64 " specified, although 'storage_inMemory' "
+                    "does not enforce such a limit.", max_size);
+    }
+
+    try
+    {
+        switch (model)
+        {
+        case CACHE_THREAD_MODEL_ST:
+            pStorage = reinterpret_cast<CACHE_STORAGE*>(InMemoryStorageST::create(zname, ttl, argc, argv));
+            break;
+
+        default:
+            MXS_ERROR("Unknown thread model %d, creating multi-thread aware storage.", (int)model);
+        case CACHE_THREAD_MODEL_MT:
+            pStorage = reinterpret_cast<CACHE_STORAGE*>(InMemoryStorageST::create(zname, ttl, argc, argv));
+        }
+
+        MXS_NOTICE("Storage module created.");
+    }
+    catch (const std::bad_alloc&)
+    {
+        MXS_OOM();
+    }
+    catch (const std::exception& x)
+    {
+        MXS_ERROR("Standard exception caught: %s", x.what());
+    }
+    catch (...)
+    {
+        MXS_ERROR("Unknown exception caught.");
+    }
+
+    return pStorage;
+}
+
+void freeInstance(CACHE_STORAGE* pinstance)
+{
+    delete reinterpret_cast<InMemoryStorage*>(pinstance);
+}
+
+cache_result_t getKey(CACHE_STORAGE* pstorage,
+                      const char* zdefault_db,
+                      const GWBUF* pquery,
+                      CACHE_KEY* pkey)
+{
+    ss_dassert(pstorage);
+    // zdefault_db may be NULL.
+    ss_dassert(pquery);
+    ss_dassert(pkey);
+
+    cache_result_t result = CACHE_RESULT_ERROR;
+
+    try
+    {
+        result = reinterpret_cast<InMemoryStorage*>(pstorage)->get_key(zdefault_db, pquery, pkey);
+    }
+    catch (const std::bad_alloc&)
+    {
+        MXS_OOM();
+    }
+    catch (const std::exception& x)
+    {
+        MXS_ERROR("Standard exception caught: %s", x.what());
+    }
+    catch (...)
+    {
+        MXS_ERROR("Unknown exception caught.");
+    }
+
+    return result;
+}
+
+cache_result_t getValue(CACHE_STORAGE* pstorage,
+                        const CACHE_KEY* pkey,
+                        uint32_t flags,
+                        GWBUF** ppresult)
+{
+    ss_dassert(pstorage);
+    ss_dassert(pkey);
+    ss_dassert(ppresult);
+
+    cache_result_t result = CACHE_RESULT_ERROR;
+
+    try
+    {
+        result = reinterpret_cast<InMemoryStorage*>(pstorage)->get_value(*pkey, flags, ppresult);
+    }
+    catch (const std::bad_alloc&)
+    {
+        MXS_OOM();
+    }
+    catch (const std::exception& x)
+    {
+        MXS_ERROR("Standard exception caught: %s", x.what());
+    }
+    catch (...)
+    {
+        MXS_ERROR("Unknown exception caught.");
+    }
+
+    return result;
+}
+
+cache_result_t putValue(CACHE_STORAGE* pstorage,
+                        const CACHE_KEY* pkey,
+                        const GWBUF* pvalue)
+{
+    ss_dassert(pstorage);
+    ss_dassert(pkey);
+    ss_dassert(pvalue);
+
+    cache_result_t result = CACHE_RESULT_ERROR;
+
+    try
+    {
+        result = reinterpret_cast<InMemoryStorage*>(pstorage)->put_value(*pkey, pvalue);
+    }
+    catch (const std::bad_alloc&)
+    {
+        MXS_OOM();
+    }
+    catch (const std::exception& x)
+    {
+        MXS_ERROR("Standard exception caught: %s", x.what());
+    }
+    catch (...)
+    {
+        MXS_ERROR("Unknown exception caught.");
+    }
+
+    return result;
+}
+
+cache_result_t delValue(CACHE_STORAGE* pstorage,
+                        const CACHE_KEY* pkey)
+{
+    ss_dassert(pstorage);
+    ss_dassert(pkey);
+
+    cache_result_t result = CACHE_RESULT_ERROR;
+
+    try
+    {
+        result = reinterpret_cast<InMemoryStorage*>(pstorage)->del_value(*pkey);
+    }
+    catch (const std::bad_alloc&)
+    {
+        MXS_OOM();
+    }
+    catch (const std::exception& x)
+    {
+        MXS_ERROR("Standard exception caught: %s", x.what());
+    }
+    catch (...)
+    {
+        MXS_ERROR("Unknown exception caught.");
+    }
+
+    return result;
+}
+
+}
+
+extern "C"
+{
+
+CACHE_STORAGE_API* CacheGetStorageAPI()
+{
+    static CACHE_STORAGE_API api =
+        {
+            initialize,
+            createInstance,
+            freeInstance,
+            getKey,
+            getValue,
+            putValue,
+            delValue,
+        };
+
+    return &api;
+}
+
+}