diff --git a/core/CMakeLists.txt b/core/CMakeLists.txt
index a4b641897..e61734e1f 100644
--- a/core/CMakeLists.txt
+++ b/core/CMakeLists.txt
@@ -1,6 +1,8 @@
-add_library(dfly_core  compact_object.cc dragonfly_core.cc tx_queue.cc)
-cxx_link(dfly_core base absl::flat_hash_map redis_lib)
+add_library(dfly_core  compact_object.cc dragonfly_core.cc interpreter.cc 
+            tx_queue.cc)
+cxx_link(dfly_core base absl::flat_hash_map redis_lib TRDP::lua crypto)
 
 cxx_test(dfly_core_test dfly_core LABELS DFLY)
 cxx_test(compact_object_test dfly_core LABELS DFLY)
-cxx_test(dash_test dfly_core LABELS DFLY)
\ No newline at end of file
+cxx_test(dash_test dfly_core LABELS DFLY)
+cxx_test(interpreter_test dfly_core LABELS DFLY)
diff --git a/core/interpreter.cc b/core/interpreter.cc
new file mode 100644
index 000000000..7b1a97305
--- /dev/null
+++ b/core/interpreter.cc
@@ -0,0 +1,170 @@
+// Copyright 2022, Roman Gershman.  All rights reserved.
+// See LICENSE for licensing terms.
+//
+
+#include "core/interpreter.h"
+
+#include <absl/strings/str_cat.h>
+#include <openssl/sha.h>
+
+#include <cstring>
+
+extern "C" {
+#include <lauxlib.h>
+#include <lua.h>
+#include <lualib.h>
+}
+
+#include "base/logging.h"
+
+namespace dfly {
+using namespace std;
+
+namespace {
+
+void RunSafe(lua_State* lua, string_view buf, const char* name) {
+  CHECK_EQ(0, luaL_loadbuffer(lua, buf.data(), buf.size(), name));
+  int err = lua_pcall(lua, 0, 0, 0);
+  if (err) {
+    const char* errstr = lua_tostring(lua, -1);
+    LOG(FATAL) << "Error running " << name << " " << errstr;
+  }
+}
+
+void Require(lua_State* lua, const char* name, lua_CFunction openf) {
+  luaL_requiref(lua, name, openf, 1);
+  lua_pop(lua, 1); /* remove lib */
+}
+
+void InitLua(lua_State* lua) {
+  Require(lua, "", luaopen_base);
+  Require(lua, LUA_TABLIBNAME, luaopen_table);
+  Require(lua, LUA_STRLIBNAME, luaopen_string);
+  Require(lua, LUA_MATHLIBNAME, luaopen_math);
+  Require(lua, LUA_DBLIBNAME, luaopen_debug);
+
+  /* Add a helper function we use for pcall error reporting.
+   * Note that when the error is in the C function we want to report the
+   * information about the caller, that's what makes sense from the point
+   * of view of the user debugging a script. */
+  {
+    const char errh_func[] =
+        "local dbg = debug\n"
+        "function __redis__err__handler(err)\n"
+        "  local i = dbg.getinfo(2,'nSl')\n"
+        "  if i and i.what == 'C' then\n"
+        "    i = dbg.getinfo(3,'nSl')\n"
+        "  end\n"
+        "  if i then\n"
+        "    return i.source .. ':' .. i.currentline .. ': ' .. err\n"
+        "  else\n"
+        "    return err\n"
+        "  end\n"
+        "end\n";
+    RunSafe(lua, errh_func, "@err_handler_def");
+  }
+
+  {
+    const char code[] = R"(
+local dbg=debug
+local mt = {}
+
+setmetatable(_G, mt)
+mt.__newindex = function (t, n, v)
+  if dbg.getinfo(2) then
+    local w = dbg.getinfo(2, "S").what
+    if w ~= "main" and w ~= "C" then
+      error("Script attempted to create global variable '"..tostring(n).."'", 2)
+    end
+  end
+  rawset(t, n, v)
+end
+mt.__index = function (t, n)
+  if dbg.getinfo(2) and dbg.getinfo(2, "S").what ~= "C" then
+    error("Script attempted to access nonexistent global variable '"..tostring(n).."'", 2)
+  end
+  return rawget(t, n)
+end
+debug = nil
+)";
+    RunSafe(lua, code, "@enable_strict_lua");
+  }
+}
+
+void ToHex(const uint8_t* src, char* dest) {
+  const char cset[] = "0123456789abcdef";
+  for (size_t j = 0; j < 20; j++) {
+    dest[j * 2] = cset[((src[j] & 0xF0) >> 4)];
+    dest[j * 2 + 1] = cset[(src[j] & 0xF)];
+  }
+  dest[40] = '\0';
+}
+
+}  // namespace
+
+Interpreter::Interpreter() {
+  lua_ = luaL_newstate();
+  InitLua(lua_);
+}
+
+Interpreter::~Interpreter() {
+  lua_close(lua_);
+}
+
+void Interpreter::Fingerprint(string_view body, char* fp) {
+  SHA_CTX ctx;
+  uint8_t buf[20];
+
+  SHA1_Init(&ctx);
+  SHA1_Update(&ctx, body.data(), body.size());
+  SHA1_Final(buf, &ctx);
+  fp[0] = 'f';
+  fp[1] = '_';
+  ToHex(buf, fp + 2);
+}
+
+bool Interpreter::AddFunction(string_view body, string* result) {
+  char funcname[43];
+  Fingerprint(body, funcname);
+
+  string script = absl::StrCat("function ", funcname, "() \n");
+  absl::StrAppend(&script, body, "\nend");
+
+  int res = luaL_loadbuffer(lua_, script.data(), script.size(), "@user_script");
+  if (res == 0) {
+    res = lua_pcall(lua_, 0, 0, 0);  // run func definition code
+  }
+
+  if (res) {
+    result->assign(lua_tostring(lua_, -1));
+    lua_pop(lua_, 1);  // Remove the error.
+
+    return false;
+  }
+
+  result->assign(funcname);
+
+  return true;
+}
+
+bool Interpreter::RunFunction(const char* f_id, std::string* error) {
+  lua_getglobal(lua_, "__redis__err__handler");
+  int type = lua_getglobal(lua_, f_id);
+  if (type != LUA_TFUNCTION) {
+    error->assign("function not found");  // TODO: noscripterr.
+    lua_pop(lua_, 2);
+
+    return false;
+  }
+
+  /* We have zero arguments and expect
+   * a single return value. */
+  int err = lua_pcall(lua_, 0, 1, -2);
+
+  if (err) {
+    *error = lua_tostring(lua_, -1);
+  }
+  return err == 0;
+}
+
+}  // namespace dfly
diff --git a/core/interpreter.h b/core/interpreter.h
new file mode 100644
index 000000000..f7ee4ab68
--- /dev/null
+++ b/core/interpreter.h
@@ -0,0 +1,43 @@
+// Copyright 2022, Roman Gershman.  All rights reserved.
+// See LICENSE for licensing terms.
+//
+
+#pragma once
+
+#include <string_view>
+
+typedef struct lua_State lua_State;
+
+namespace dfly {
+
+class Interpreter {
+ public:
+  Interpreter();
+  ~Interpreter();
+
+  Interpreter(const Interpreter&) = delete;
+  void operator=(const Interpreter&) = delete;
+
+  // Note: We leak the state for now.
+  // Production code should not access this method.
+  lua_State* lua() {
+    return lua_;
+  }
+
+  // returns false if an error happenned, sets error string into result.
+  // otherwise, returns true and sets result to function id.
+  bool AddFunction(std::string_view body, std::string* result);
+
+  // Runs already added function f_id returned by a successful call to AddFunction().
+  // Returns: true if the call succeeded, otherwise fills error and returns false.
+  bool RunFunction(const char* f_id, std::string* err);
+
+  // fp must point to buffer with at least 43 chars.
+  // fp[42] will be set to '\0'.
+  static void Fingerprint(std::string_view body, char* fp);
+
+ private:
+  lua_State* lua_;
+};
+
+}  // namespace dfly
diff --git a/core/interpreter_test.cc b/core/interpreter_test.cc
new file mode 100644
index 000000000..e3cb37bf5
--- /dev/null
+++ b/core/interpreter_test.cc
@@ -0,0 +1,67 @@
+// Copyright 2022, Roman Gershman.  All rights reserved.
+// See LICENSE for licensing terms.
+//
+
+#include "core/interpreter.h"
+
+extern "C" {
+#include <lauxlib.h>
+#include <lua.h>
+}
+
+#include <gmock/gmock.h>
+
+#include "base/gtest.h"
+#include "base/logging.h"
+
+namespace dfly {
+using namespace std;
+
+class InterpreterTest : public ::testing::Test {
+ protected:
+  InterpreterTest() {
+  }
+
+  lua_State* lua() {
+    return intptr_.lua();
+  }
+
+  void RunInline(string_view buf, const char* name) {
+    CHECK_EQ(0, luaL_loadbuffer(lua(), buf.data(), buf.size(), name));
+    CHECK_EQ(0, lua_pcall(lua(), 0, 0, 0));
+  }
+
+  Interpreter intptr_;
+};
+
+TEST_F(InterpreterTest, Basic) {
+  RunInline(R"(
+    function foo(n)
+      return n,n+1
+    end)",
+            "code1");
+
+  int type = lua_getglobal(lua(), "foo");
+  ASSERT_EQ(LUA_TFUNCTION, type);
+  lua_pushnumber(lua(), 42);
+  lua_pcall(lua(), 1, 2, 0);
+  int val1 = lua_tointeger(lua(), -1);
+  int val2 = lua_tointeger(lua(), -2);
+  lua_pop(lua(), 2);
+
+  EXPECT_EQ(43, val1);
+  EXPECT_EQ(42, val2);
+  EXPECT_EQ(0, lua_gettop(lua()));
+}
+
+TEST_F(InterpreterTest, Add) {
+  string res1, res2;
+
+  EXPECT_TRUE(intptr_.AddFunction("return 0", &res1));
+  EXPECT_EQ(0, lua_gettop(lua()));
+  EXPECT_FALSE(intptr_.AddFunction("foobar", &res2));
+  EXPECT_THAT(res2, testing::HasSubstr("syntax error"));
+  EXPECT_EQ(0, lua_gettop(lua()));
+}
+
+}  // namespace dfly
diff --git a/helio b/helio
index 3ee017cce..a300a704e 160000
--- a/helio
+++ b/helio
@@ -1 +1 @@
-Subproject commit 3ee017cce280493c845a010a28caa4cf1d0f4e9b
+Subproject commit a300a704e193d115333f41a81438ba74d3df8c51
diff --git a/server/CMakeLists.txt b/server/CMakeLists.txt
index 2947714de..892c47cd0 100644
--- a/server/CMakeLists.txt
+++ b/server/CMakeLists.txt
@@ -24,4 +24,5 @@ cxx_test(rdb_test dfly_test_lib DATA testdata/empty.rdb testdata/small.rdb LABEL
 
 add_custom_target(check_dfly WORKING_DIRECTORY .. COMMAND ctest -L DFLY)
 add_dependencies(check_dfly dragonfly_test list_family_test
-                 generic_family_test memcache_parser_test redis_parser_test string_family_test)
+                 generic_family_test memcache_parser_test rdb_test 
+                 redis_parser_test string_family_test)
diff --git a/server/common.cc b/server/common.cc
index fe5e5b1e7..ecd404079 100644
--- a/server/common.cc
+++ b/server/common.cc
@@ -7,7 +7,6 @@
 #include "base/logging.h"
 #include "server/common_types.h"
 #include "server/error.h"
-#include "server/global_state.h"
 #include "server/server_state.h"
 
 namespace dfly {
@@ -22,6 +21,23 @@ ServerState::ServerState() {
 ServerState::~ServerState() {
 }
 
+void ServerState::Init() {
+  gstate_ = GlobalState::IDLE;
+}
+
+void ServerState::Shutdown() {
+  gstate_ = GlobalState::SHUTTING_DOWN;
+  interpreter_.reset();
+}
+
+Interpreter& ServerState::GetInterpreter() {
+  if (!interpreter_) {
+    interpreter_.emplace();
+  }
+
+  return interpreter_.value();
+}
+
 #define ADD(x) (x) += o.x
 
 ConnectionStats& ConnectionStats::operator+=(const ConnectionStats& o) {
diff --git a/server/conn_context.h b/server/conn_context.h
index 31ee31fd9..ad4ac6bfe 100644
--- a/server/conn_context.h
+++ b/server/conn_context.h
@@ -31,6 +31,10 @@ struct ConnectionState {
   enum Mask : uint32_t {
     ASYNC_DISPATCH = 1,  // whether a command is handled via async dispatch.
     CONN_CLOSING = 2,    // could be because of unrecoverable error or planned action.
+
+    // Whether this connection belongs to replica, i.e. a dragonfly slave is connected to this
+    // host (master) via this connection to sync from it.
+    REPL_CONNECTION = 2,
   };
 
   uint32_t mask = 0;  // A bitmask of Mask values.
diff --git a/server/dragonfly_connection.cc b/server/dragonfly_connection.cc
index b033c66b0..c5fb4779d 100644
--- a/server/dragonfly_connection.cc
+++ b/server/dragonfly_connection.cc
@@ -280,6 +280,11 @@ finish:
 
   stats->read_buf_capacity -= io_buf_.Capacity();
 
+  // Update num_replicas if this was a replica connection.
+  if (cc_->conn_state.mask & ConnectionState::REPL_CONNECTION) {
+    --stats->num_replicas;
+  }
+
   if (cc_->ec()) {
     ec = cc_->ec();
   } else {
diff --git a/server/main_service.cc b/server/main_service.cc
index 023a77e03..01da07431 100644
--- a/server/main_service.cc
+++ b/server/main_service.cc
@@ -72,6 +72,8 @@ void Service::Init(util::AcceptServer* acceptor, const InitOpts& opts) {
   shard_set_.Init(shard_num);
 
   pp_.Await([&](uint32_t index, ProactorBase* pb) {
+    ServerState::tlocal()->Init();
+
     if (index < shard_count()) {
       shard_set_.InitThreadLocal(pb, !opts.disable_time_update);
     }
@@ -96,6 +98,8 @@ void Service::Shutdown() {
   request_latency_usec.Shutdown();
   ping_qps.Shutdown();
 
+   pp_.AwaitFiberOnAll([](ProactorBase* pb) { ServerState::tlocal()->Shutdown(); });
+
   // to shutdown all the runtime components that depend on EngineShard.
   server_family_.Shutdown();
   StringFamily::Shutdown();
@@ -129,7 +133,20 @@ void Service::DispatchCommand(CmdArgList args, ConnectionContext* cntx) {
     return cntx->SendError(absl::StrCat("unknown command `", cmd_str, "`"));
   }
 
+  if (etl.gstate() == GlobalState::LOADING || etl.gstate() == GlobalState::SHUTTING_DOWN) {
+    string err = absl::StrCat("Can not execute during ", GlobalState::Name(etl.gstate()));
+    cntx->SendError(err);
+    return;
+  }
+
+  bool is_write_cmd = cid->opt_mask() & CO::WRITE;
   bool under_multi = cntx->conn_state.exec_state != ConnectionState::EXEC_INACTIVE && !is_trans_cmd;
+
+  if (!etl.is_master && is_write_cmd) {
+    cntx->SendError("-READONLY You can't write against a read only replica.");
+    return;
+  }
+
   if ((cid->arity() > 0 && args.size() != size_t(cid->arity())) ||
       (cid->arity() < 0 && args.size() < size_t(-cid->arity()))) {
     return cntx->SendError(WrongNumArgsError(cmd_str));
@@ -272,6 +289,12 @@ void Service::Multi(CmdArgList args, ConnectionContext* cntx) {
   return cntx->SendOk();
 }
 
+void Service::Eval(CmdArgList args, ConnectionContext* cntx) {
+  Interpreter& script = ServerState::tlocal()->GetInterpreter();
+  script.lua();
+  return cntx->SendOk();
+}
+
 void Service::Exec(CmdArgList args, ConnectionContext* cntx) {
   if (cntx->conn_state.exec_state == ConnectionState::EXEC_INACTIVE) {
     return cntx->SendError("EXEC without MULTI");
@@ -315,9 +338,12 @@ void Service::Exec(CmdArgList args, ConnectionContext* cntx) {
 VarzValue::Map Service::GetVarzStats() {
   VarzValue::Map res;
 
-  atomic_ulong num_keys{0};
-  shard_set_.RunBriefInParallel([&](EngineShard* es) { num_keys += es->db_slice().DbSize(0); });
-  res.emplace_back("keys", VarzValue::FromInt(num_keys.load()));
+  Metrics m = server_family_.GetMetrics();
+
+  res.emplace_back("keys", VarzValue::FromInt(m.db.key_count));
+  res.emplace_back("obj_mem_usage", VarzValue::FromInt(m.db.obj_memory_usage));
+  double load = double(m.db.key_count) / (1 + m.db.bucket_count);
+  res.emplace_back("table_load_factor", VarzValue::FromDouble(load));
 
   return res;
 }
@@ -338,6 +364,7 @@ void Service::RegisterCommands() {
   registry_ << CI{"QUIT", CO::READONLY | CO::FAST, 1, 0, 0, 0}.HFUNC(Quit)
             << CI{"MULTI", CO::NOSCRIPT | CO::FAST | CO::LOADING | CO::STALE, 1, 0, 0, 0}.HFUNC(
                    Multi)
+            << CI{"EVAL", CO::NOSCRIPT, -3, 0, 0, 0}.HFUNC(Eval)
             << CI{"EXEC", kExecMask, 1, 0, 0, 0}.SetHandler(cb_exec);
 
   StringFamily::Register(&registry_);
diff --git a/server/main_service.h b/server/main_service.h
index 253b06cfa..a1d16ca66 100644
--- a/server/main_service.h
+++ b/server/main_service.h
@@ -64,6 +64,8 @@ class Service {
  private:
   static void Quit(CmdArgList args, ConnectionContext* cntx);
   static void Multi(CmdArgList args, ConnectionContext* cntx);
+  static void Eval(CmdArgList args, ConnectionContext* cntx);
+
   void Exec(CmdArgList args, ConnectionContext* cntx);
 
 
diff --git a/server/server_family.cc b/server/server_family.cc
index e73305257..9c8797064 100644
--- a/server/server_family.cc
+++ b/server/server_family.cc
@@ -63,6 +63,7 @@ error_code CreateDirs(fs::path dir_path) {
   }
   return ec;
 }
+
 }  // namespace
 
 ServerFamily::ServerFamily(Service* engine)
@@ -80,6 +81,7 @@ void ServerFamily::Init(util::AcceptServer* acceptor) {
 
 void ServerFamily::Shutdown() {
   VLOG(1) << "ServerFamily::Shutdown";
+
   pp_.GetNextProactor()->Await([this] {
     unique_lock lk(replica_of_mu_);
     if (replica_) {
@@ -176,7 +178,7 @@ void ServerFamily::Save(CmdArgList args, ConnectionContext* cntx) {
     return;
   }
 
-  pp_.Await([](auto*) { ServerState::tlocal()->state = GlobalState::SAVING; });
+  pp_.Await([](auto*) { ServerState::tlocal()->set_gstate(GlobalState::SAVING); });
 
   unique_ptr<::io::WriteFile> wf(*res);
   auto start = absl::Now();
@@ -200,7 +202,7 @@ void ServerFamily::Save(CmdArgList args, ConnectionContext* cntx) {
     return;
   }
 
-  pp_.Await([](auto*) { ServerState::tlocal()->state = GlobalState::IDLE; });
+  pp_.Await([](auto*) { ServerState::tlocal()->set_gstate(GlobalState::IDLE); });
   CHECK_EQ(GlobalState::SAVING, global_state_.Clear());
 
   absl::Duration dur = absl::Now() - start;
@@ -243,7 +245,7 @@ Metrics ServerFamily::GetMetrics() const {
 void ServerFamily::Info(CmdArgList args, ConnectionContext* cntx) {
   const char kInfo1[] =
       R"(# Server
-redis_version:6.2.0
+redis_version:1.9.9
 redis_mode:standalone
 arch_bits:64
 multiplexing_api:iouring
@@ -292,6 +294,9 @@ tcp_port:)";
     absl::StrAppend(&info, "master_last_io_seconds_ago:", rinfo.master_last_io_sec, "\n");
     absl::StrAppend(&info, "master_sync_in_progress:", rinfo.sync_in_progress, "\n");
   }
+  absl::StrAppend(&info, "\n# Keyspace\n");
+  absl::StrAppend(&info, "db0:keys=xxx,expires=yyy,avg_ttl=zzz\n");  // TODO
+
   cntx->SendBulkString(info);
 }
 
@@ -308,7 +313,6 @@ void ServerFamily::ReplicaOf(CmdArgList args, ConnectionContext* cntx) {
       auto repl_ptr = replica_;
       CHECK(repl_ptr);
 
-
       pp_.AwaitFiberOnAll([&](util::ProactorBase* pb) { ServerState::tlocal()->is_master = true; });
       replica_->Stop();
       replica_.reset();
@@ -378,6 +382,8 @@ void ServerFamily::SyncGeneric(std::string_view repl_master_id, uint64_t offs,
     return;
   }
 
+  cntx->conn_state.mask |= ConnectionState::REPL_CONNECTION;
+  ServerState::tl_connection_stats()->num_replicas += 1;
   // TBD.
 }
 
diff --git a/server/server_state.h b/server/server_state.h
index 002bb9f70..de6d8c578 100644
--- a/server/server_state.h
+++ b/server/server_state.h
@@ -4,10 +4,12 @@
 
 #pragma once
 
+#include <optional>
 #include <vector>
 
 #include "server/common_types.h"
 #include "server/global_state.h"
+#include "core/interpreter.h"
 
 namespace dfly {
 
@@ -32,7 +34,9 @@ class ServerState {  // public struct - to allow initialization.
   ServerState();
   ~ServerState();
 
-  GlobalState::S state = GlobalState::IDLE;
+  void Init();
+  void Shutdown();
+
   bool is_master = true;
 
   ConnectionStats connection_stats;
@@ -49,8 +53,15 @@ class ServerState {  // public struct - to allow initialization.
     return live_transactions_;
   }
 
+  GlobalState::S gstate() const { return gstate_;}
+  void set_gstate(GlobalState::S s) { gstate_ = s; }
+
+  Interpreter& GetInterpreter();
+
  private:
   int64_t live_transactions_ = 0;
+  std::optional<Interpreter> interpreter_;
+  GlobalState::S gstate_ = GlobalState::IDLE;
 
   static thread_local ServerState state_;
 };