diff --git a/.clang-format b/.clang-format
new file mode 100644
index 0000000..bf80c11
--- /dev/null
+++ b/.clang-format
@@ -0,0 +1,19 @@
+# ---
+# We'll use defaults from the Google style, but with 2 columns indentation.
+BasedOnStyle: Google
+IndentWidth: 2
+ColumnLimit: 100
+---
+Language: Cpp
+AllowShortLoopsOnASingleLine: false
+AllowShortFunctionsOnASingleLine: false
+AllowShortIfStatementsOnASingleLine: false
+AlwaysBreakTemplateDeclarations: false
+ConstructorInitializerAllOnOneLineOrOnePerLine: false
+DerivePointerAlignment: false
+PointerAlignment: Left
+BasedOnStyle: Google
+ColumnLimit: 100
+---
+Language: Proto
+BasedOnStyle: Google
diff --git a/server/CMakeLists.txt b/server/CMakeLists.txt
index 651f46e..78144bd 100644
--- a/server/CMakeLists.txt
+++ b/server/CMakeLists.txt
@@ -1,7 +1,13 @@
 add_executable(dragonfly dfly_main.cc)
 cxx_link(dragonfly base dragonfly_lib)
 
-add_library(dragonfly_lib dragonfly_listener.cc dragonfly_connection.cc main_service.cc)
+add_library(dragonfly_lib dragonfly_listener.cc dragonfly_connection.cc main_service.cc
+            redis_parser.cc resp_expr.cc)
 
 cxx_link(dragonfly_lib uring_fiber_lib
          fibers_ext strings_lib http_server_lib)
+
+add_library(dfly_test_lib test_utils.cc)
+cxx_link(dfly_test_lib dragonfly_lib gtest_main_ext)
+
+cxx_test(redis_parser_test dfly_test_lib LABELS DFLY)
diff --git a/server/redis_parser.cc b/server/redis_parser.cc
new file mode 100644
index 0000000..8cfc09b
--- /dev/null
+++ b/server/redis_parser.cc
@@ -0,0 +1,389 @@
+// Copyright 2021, Beeri 15.  All rights reserved.
+// Author: Roman Gershman (romange@gmail.com)
+//
+#include "server/redis_parser.h"
+
+#include <absl/strings/numbers.h>
+
+#include "base/logging.h"
+
+namespace dfly {
+
+using namespace std;
+
+namespace {
+
+constexpr int kMaxArrayLen = 1024;
+constexpr int64_t kMaxBulkLen = 64 * (1ul << 20);  // 64MB.
+
+}  // namespace
+
+auto RedisParser::Parse(Buffer str, uint32_t* consumed, RespExpr::Vec* res) -> Result {
+  *consumed = 0;
+  res->clear();
+
+  if (str.size() < 2) {
+    return INPUT_PENDING;
+  }
+
+  if (state_ == CMD_COMPLETE_S) {
+    state_ = INIT_S;
+  }
+
+  if (state_ == INIT_S) {
+    InitStart(str[0], res);
+  }
+
+  if (!cached_expr_)
+    cached_expr_ = res;
+
+  while (state_ != CMD_COMPLETE_S) {
+    last_consumed_ = 0;
+    switch (state_) {
+      case ARRAY_LEN_S:
+        last_result_ = ConsumeArrayLen(str);
+        break;
+      case PARSE_ARG_S:
+        if (str.size() < 4) {
+          last_result_ = INPUT_PENDING;
+        } else {
+          last_result_ = ParseArg(str);
+        }
+        break;
+      case INLINE_S:
+        DCHECK(parse_stack_.empty());
+        last_result_ = ParseInline(str);
+        break;
+      case BULK_STR_S:
+        last_result_ = ConsumeBulk(str);
+        break;
+      case FINISH_ARG_S:
+        HandleFinishArg();
+        break;
+      default:
+        LOG(FATAL) << "Unexpected state " << int(state_);
+    }
+
+    *consumed += last_consumed_;
+
+    if (last_result_ != OK) {
+      break;
+    }
+    str.remove_prefix(last_consumed_);
+  }
+
+  if (last_result_ == INPUT_PENDING) {
+    StashState(res);
+  } else if (last_result_ == OK) {
+    DCHECK(cached_expr_);
+    if (res != cached_expr_) {
+      DCHECK(!stash_.empty());
+
+      *res = *cached_expr_;
+    }
+  }
+
+  return last_result_;
+}
+
+void RedisParser::InitStart(uint8_t prefix_b, RespExpr::Vec* res) {
+  buf_stash_.clear();
+  stash_.clear();
+  cached_expr_ = res;
+  parse_stack_.clear();
+  last_stashed_level_ = 0;
+  last_stashed_index_ = 0;
+
+  switch (prefix_b) {
+    case '$':
+      state_ = PARSE_ARG_S;
+      parse_stack_.emplace_back(1, cached_expr_);  // expression of length 1.
+      break;
+    case '*':
+      state_ = ARRAY_LEN_S;
+      break;
+    default:
+      state_ = INLINE_S;
+      break;
+  }
+}
+
+void RedisParser::StashState(RespExpr::Vec* res) {
+  if (cached_expr_->empty() && stash_.empty()) {
+    cached_expr_ = nullptr;
+    return;
+  }
+
+  if (cached_expr_ == res) {
+    stash_.emplace_back(new RespExpr::Vec(*res));
+    cached_expr_ = stash_.back().get();
+  }
+
+  DCHECK_LT(last_stashed_level_, stash_.size());
+  while (true) {
+    auto& cur = *stash_[last_stashed_level_];
+
+    for (; last_stashed_index_ < cur.size(); ++last_stashed_index_) {
+      auto& e = cur[last_stashed_index_];
+      if (RespExpr::STRING == e.type) {
+        Buffer& ebuf = get<Buffer>(e.u);
+        if (ebuf.empty() && last_stashed_index_ + 1 == cur.size())
+          break;
+        if (!ebuf.empty() && !e.has_support) {
+          BlobPtr ptr(new uint8_t[ebuf.size()]);
+          memcpy(ptr.get(), ebuf.data(), ebuf.size());
+          ebuf = Buffer{ptr.get(), ebuf.size()};
+          buf_stash_.push_back(std::move(ptr));
+          e.has_support = true;
+        }
+      }
+    }
+
+    if (last_stashed_level_ + 1 == stash_.size())
+      break;
+    ++last_stashed_level_;
+    last_stashed_index_ = 0;
+  }
+}
+
+auto RedisParser::ParseInline(Buffer str) -> Result {
+  DCHECK(!str.empty());
+
+  uint8_t* ptr = str.begin();
+  uint8_t* end = str.end();
+  uint8_t* token_start = ptr;
+
+  if (is_broken_token_) {
+    while (ptr != end && *ptr > 32)
+      ++ptr;
+
+    size_t len = ptr - token_start;
+
+    ExtendLastString(Buffer(token_start, len));
+    if (ptr != end) {
+      is_broken_token_ = false;
+    }
+  }
+
+  auto is_finish = [&] { return ptr == end || *ptr == '\n'; };
+
+  while (true) {
+    while (!is_finish() && *ptr <= 32) {
+      ++ptr;
+    }
+    // We do not test for \r in order to accept 'nc' input.
+    if (is_finish())
+      break;
+
+    DCHECK(!is_broken_token_);
+
+    token_start = ptr;
+    while (ptr != end && *ptr > 32)
+      ++ptr;
+
+    cached_expr_->emplace_back(RespExpr::STRING);
+    cached_expr_->back().u = Buffer{token_start, size_t(ptr - token_start)};
+  }
+
+  last_consumed_ = ptr - str.data();
+  if (ptr == end) {  // we have not finished parsing.
+    if (ptr[-1] > 32) {
+      // we stopped in the middle of the token.
+      is_broken_token_ = true;
+    }
+
+    return INPUT_PENDING;
+  } else {
+    ++last_consumed_;  // consume the delimiter as well.
+  }
+  state_ = CMD_COMPLETE_S;
+
+  return OK;
+}
+
+auto RedisParser::ParseNum(Buffer str, int64_t* res) -> Result {
+  if (str.size() < 4) {
+    return INPUT_PENDING;
+  }
+
+  char* s = reinterpret_cast<char*>(str.data() + 1);
+  char* pos = reinterpret_cast<char*>(memchr(s, '\n', str.size() - 1));
+  if (!pos) {
+    return str.size() < 32 ? INPUT_PENDING : BAD_INT;
+  }
+  if (pos[-1] != '\r') {
+    return BAD_INT;
+  }
+
+  bool success = absl::SimpleAtoi(std::string_view{s, size_t(pos - s - 1)}, res);
+  if (!success) {
+    return BAD_INT;
+  }
+  last_consumed_ = (pos - s) + 2;
+
+  return OK;
+}
+
+auto RedisParser::ConsumeArrayLen(Buffer str) -> Result {
+  int64_t len;
+
+  Result res = ParseNum(str, &len);
+  switch (res) {
+    case INPUT_PENDING:
+      return INPUT_PENDING;
+    case BAD_INT:
+      return BAD_ARRAYLEN;
+    case OK:
+      if (len < -1 || len > kMaxArrayLen)
+        return BAD_ARRAYLEN;
+      break;
+    default:
+      LOG(ERROR) << "Unexpected result " << res;
+  }
+
+  // Already parsed array expression somewhere. Server should accept only single-level expressions.
+  if (!parse_stack_.empty())
+    return BAD_STRING;
+
+  // Similarly if our cached expr is not empty.
+  if (!cached_expr_->empty())
+    return BAD_STRING;
+
+  if (len <= 0) {
+    cached_expr_->emplace_back(len == -1 ? RespExpr::NIL_ARRAY : RespExpr::ARRAY);
+    if (len < 0)
+      cached_expr_->back().u.emplace<RespVec*>(nullptr);  // nil
+    else {
+      static RespVec empty_vec;
+      cached_expr_->back().u = &empty_vec;
+    }
+    state_ = (parse_stack_.empty()) ? CMD_COMPLETE_S : FINISH_ARG_S;
+
+    return OK;
+  }
+
+  parse_stack_.emplace_back(len, cached_expr_);
+  DCHECK(cached_expr_->empty());
+  state_ = PARSE_ARG_S;
+
+  return OK;
+}
+
+auto RedisParser::ParseArg(Buffer str) -> Result {
+  char c = str[0];
+  if (c == '$') {
+    int64_t len;
+
+    Result res = ParseNum(str, &len);
+    switch (res) {
+      case INPUT_PENDING:
+        return INPUT_PENDING;
+      case BAD_INT:
+        return BAD_ARRAYLEN;
+      case OK:
+        if (len < -1 || len > kMaxBulkLen)
+          return BAD_ARRAYLEN;
+        break;
+      default:
+        LOG(ERROR) << "Unexpected result " << res;
+    }
+
+    if (len < 0) {
+      state_ = FINISH_ARG_S;
+      cached_expr_->emplace_back(RespExpr::NIL);
+    } else {
+      cached_expr_->emplace_back(RespExpr::STRING);
+      bulk_len_ = len;
+      state_ = BULK_STR_S;
+    }
+    cached_expr_->back().u = Buffer{};
+
+    return OK;
+  }
+
+  return BAD_BULKLEN;
+}
+
+auto RedisParser::ConsumeBulk(Buffer str) -> Result {
+  auto& bulk_str = get<Buffer>(cached_expr_->back().u);
+
+  if (str.size() >= bulk_len_ + 2) {
+    if (str[bulk_len_] != '\r' || str[bulk_len_ + 1] != '\n') {
+      return BAD_STRING;
+    }
+
+    if (bulk_len_) {
+      if (is_broken_token_) {
+        memcpy(bulk_str.end(), str.data(), bulk_len_);
+        bulk_str = Buffer{bulk_str.data(), bulk_str.size() + bulk_len_};
+      } else {
+        bulk_str = str.subspan(0, bulk_len_);
+      }
+    }
+    is_broken_token_ = false;
+    state_ = FINISH_ARG_S;
+    last_consumed_ = bulk_len_ + 2;
+    bulk_len_ = 0;
+
+    return OK;
+  }
+
+  if (str.size() >= 32) {
+    DCHECK(bulk_len_);
+    size_t len = std::min<size_t>(str.size(), bulk_len_);
+
+    if (is_broken_token_) {
+      memcpy(bulk_str.end(), str.data(), len);
+      bulk_str = Buffer{bulk_str.data(), bulk_str.size() + len};
+      DVLOG(1) << "Extending bulk stash to size " << bulk_str.size();
+    } else {
+      DVLOG(1) << "New bulk stash size " << bulk_len_;
+      std::unique_ptr<uint8_t[]> nb(new uint8_t[bulk_len_]);
+      memcpy(nb.get(), str.data(), len);
+      bulk_str = Buffer{nb.get(), len};
+      buf_stash_.emplace_back(move(nb));
+      is_broken_token_ = true;
+      cached_expr_->back().has_support = true;
+    }
+    last_consumed_ = len;
+    bulk_len_ -= len;
+  }
+
+  return INPUT_PENDING;
+}
+
+void RedisParser::HandleFinishArg() {
+  DCHECK(!parse_stack_.empty());
+  DCHECK_GT(parse_stack_.back().first, 0u);
+
+  while (true) {
+    --parse_stack_.back().first;
+    state_ = PARSE_ARG_S;
+    if (parse_stack_.back().first != 0)
+      break;
+
+    parse_stack_.pop_back();  // pop 0.
+    if (parse_stack_.empty()) {
+      state_ = CMD_COMPLETE_S;
+      break;
+    }
+    cached_expr_ = parse_stack_.back().second;
+  }
+}
+
+void RedisParser::ExtendLastString(Buffer str) {
+  DCHECK(!cached_expr_->empty() && cached_expr_->back().type == RespExpr::STRING);
+  DCHECK(!buf_stash_.empty());
+
+  Buffer& last_str = get<Buffer>(cached_expr_->back().u);
+
+  DCHECK(last_str.data() == buf_stash_.back().get());
+
+  std::unique_ptr<uint8_t[]> nb(new uint8_t[last_str.size() + str.size()]);
+  memcpy(nb.get(), last_str.data(), last_str.size());
+  memcpy(nb.get() + last_str.size(), str.data(), str.size());
+  last_str = RespExpr::Buffer{nb.get(), last_str.size() + str.size()};
+  buf_stash_.back() = std::move(nb);
+}
+
+}  // namespace dfly
diff --git a/server/redis_parser.h b/server/redis_parser.h
new file mode 100644
index 0000000..ecdc1b6
--- /dev/null
+++ b/server/redis_parser.h
@@ -0,0 +1,91 @@
+// Copyright 2021, Beeri 15.  All rights reserved.
+// Author: Roman Gershman (romange@gmail.com)
+//
+#pragma once
+
+#include <absl/container/inlined_vector.h>
+
+#include "resp_expr.h"
+
+namespace dfly {
+
+/**
+ * @brief Zero-copy (best-effort) parser.
+ *
+ */
+class RedisParser {
+ public:
+  enum Result {
+    OK,
+    INPUT_PENDING,
+    BAD_ARRAYLEN,
+    BAD_BULKLEN,
+    BAD_STRING,
+    BAD_INT
+  };
+  using Buffer = RespExpr::Buffer;
+
+  explicit RedisParser() {
+  }
+
+  /**
+   * @brief Parses str into res. "consumed" stores number of bytes consumed from str.
+   *
+   * A caller should not invalidate str if the parser returns RESP_OK as long as he continues
+   * accessing res. However, if parser returns MORE_INPUT a caller may discard consumed
+   * part of str because parser caches the intermediate state internally according to 'consumed'
+   * result.
+   *
+   * Note: A parser does not always guarantee progress, i.e. if a small buffer was passed it may
+   * returns MORE_INPUT with consumed == 0.
+   *
+   */
+
+  Result Parse(Buffer str, uint32_t* consumed, RespVec* res);
+
+  size_t stash_size() const { return stash_.size(); }
+  const std::vector<std::unique_ptr<RespVec>>& stash() const { return stash_;}
+
+ private:
+  void InitStart(uint8_t prefix_b, RespVec* res);
+  void StashState(RespVec* res);
+
+  // Skips the first character (*).
+  Result ConsumeArrayLen(Buffer str);
+  Result ParseArg(Buffer str);
+  Result ConsumeBulk(Buffer str);
+  Result ParseInline(Buffer str);
+
+  // Updates last_consumed_
+  Result ParseNum(Buffer str, int64_t* res);
+  void HandleFinishArg();
+  void ExtendLastString(Buffer str);
+
+  enum State : uint8_t {
+    INIT_S = 0,
+    INLINE_S,
+    ARRAY_LEN_S,
+    PARSE_ARG_S,  // Parse [$:+-]string\r\n
+    BULK_STR_S,
+    FINISH_ARG_S,
+    CMD_COMPLETE_S,
+  };
+
+  State state_ = INIT_S;
+  Result last_result_ = OK;
+
+  uint32_t last_consumed_ = 0;
+  uint32_t bulk_len_ = 0;
+  uint32_t last_stashed_level_ = 0, last_stashed_index_ = 0;
+
+  // expected expression length, pointer to expression vector.
+  absl::InlinedVector<std::pair<uint32_t, RespVec*>, 4> parse_stack_;
+  std::vector<std::unique_ptr<RespVec>> stash_;
+
+  using BlobPtr = std::unique_ptr<uint8_t[]>;
+  std::vector<BlobPtr> buf_stash_;
+  RespVec* cached_expr_ = nullptr;
+  bool is_broken_token_ = false;
+};
+
+}  // namespace dfly
diff --git a/server/redis_parser_test.cc b/server/redis_parser_test.cc
new file mode 100644
index 0000000..cd3869e
--- /dev/null
+++ b/server/redis_parser_test.cc
@@ -0,0 +1,126 @@
+// Copyright 2021, Beeri 15.  All rights reserved.
+// Author: Roman Gershman (romange@gmail.com)
+//
+
+#include "server/redis_parser.h"
+
+#include <absl/strings/str_cat.h>
+#include <gmock/gmock.h>
+
+#include "absl/strings/str_cat.h"
+#include "base/gtest.h"
+#include "base/logging.h"
+#include "server/test_utils.h"
+
+using namespace testing;
+using namespace std;
+namespace dfly {
+
+MATCHER_P(ArrArg, expected, absl::StrCat(negation ? "is not" : "is", " equal to:\n", expected)) {
+  if (arg.type != RespExpr::ARRAY) {
+    *result_listener << "\nWrong type: " << arg.type;
+    return false;
+  }
+  size_t exp_sz = expected;
+  size_t actual = get<RespVec*>(arg.u)->size();
+
+  if (exp_sz != actual) {
+    *result_listener << "\nActual size: " << actual;
+    return false;
+  }
+  return true;
+}
+
+class RedisParserTest : public testing::Test {
+ protected:
+  RedisParser::Result Parse(std::string_view str);
+
+  RedisParser parser_;
+  RespExpr::Vec args_;
+  uint32_t consumed_;
+
+  unique_ptr<uint8_t[]> stash_;
+};
+
+RedisParser::Result RedisParserTest::Parse(std::string_view str) {
+  stash_.reset(new uint8_t[str.size()]);
+  auto* ptr = stash_.get();
+  memcpy(ptr, str.data(), str.size());
+  return parser_.Parse(RedisParser::Buffer{ptr, str.size()}, &consumed_, &args_);
+}
+
+TEST_F(RedisParserTest, Inline) {
+  RespExpr e{RespExpr::STRING};
+  ASSERT_EQ(RespExpr::STRING, e.type);
+
+  const char kCmd1[] = "KEY   VAL\r\n";
+
+  ASSERT_EQ(RedisParser::OK, Parse(kCmd1));
+  EXPECT_EQ(strlen(kCmd1), consumed_);
+  EXPECT_THAT(args_, ElementsAre(StrArg("KEY"), StrArg("VAL")));
+
+  ASSERT_EQ(RedisParser::INPUT_PENDING, Parse("KEY"));
+  EXPECT_EQ(3, consumed_);
+  ASSERT_EQ(RedisParser::INPUT_PENDING, Parse(" FOO "));
+  EXPECT_EQ(5, consumed_);
+  ASSERT_EQ(RedisParser::INPUT_PENDING, Parse(" BAR"));
+  EXPECT_EQ(4, consumed_);
+  ASSERT_EQ(RedisParser::OK, Parse(" \r\n "));
+  EXPECT_EQ(3, consumed_);
+  EXPECT_THAT(args_, ElementsAre(StrArg("KEY"), StrArg("FOO"), StrArg("BAR")));
+
+  ASSERT_EQ(RedisParser::INPUT_PENDING, Parse(" 1 2"));
+  EXPECT_EQ(4, consumed_);
+  ASSERT_EQ(RedisParser::INPUT_PENDING, Parse(" 45"));
+  EXPECT_EQ(3, consumed_);
+  ASSERT_EQ(RedisParser::OK, Parse("\r\n"));
+  EXPECT_EQ(2, consumed_);
+  EXPECT_THAT(args_, ElementsAre(StrArg("1"), StrArg("2"), StrArg("45")));
+
+  // Empty queries return RESP_OK.
+  EXPECT_EQ(RedisParser::OK, Parse("\r\n"));
+  EXPECT_EQ(2, consumed_);
+}
+
+TEST_F(RedisParserTest, InlineEscaping) {
+  LOG(ERROR)  << "TBD: to be compliant with sdssplitargs";  // TODO:
+}
+
+TEST_F(RedisParserTest, Multi1) {
+  ASSERT_EQ(RedisParser::INPUT_PENDING, Parse("*1\r\n$"));
+  EXPECT_EQ(4, consumed_);
+
+  ASSERT_EQ(RedisParser::INPUT_PENDING, Parse("$4\r\nMSET"));
+  EXPECT_EQ(4, consumed_);
+
+  ASSERT_EQ(RedisParser::OK, Parse("MSET\r\n*2\r\n"));
+  EXPECT_EQ(6, consumed_);
+
+  ASSERT_EQ(RedisParser::INPUT_PENDING, Parse("*2\r\n$3\r\nKEY\r\n$3\r\nVAL"));
+  EXPECT_EQ(17, consumed_);
+
+  ASSERT_EQ(RedisParser::OK, Parse("VAL\r\n"));
+  EXPECT_EQ(5, consumed_);
+  EXPECT_THAT(args_, ElementsAre("KEY", "VAL"));
+}
+
+TEST_F(RedisParserTest, Multi2) {
+  const char kFirst[] = "*3\r\n$3\r\nSET\r\n$16\r\nkey:";
+  const char kSecond[] = "key:000002273458\r\n$3\r\nVXK";
+  ASSERT_EQ(RedisParser::INPUT_PENDING, Parse(kFirst));
+  ASSERT_EQ(strlen(kFirst) - 4, consumed_);
+  ASSERT_EQ(RedisParser::INPUT_PENDING, Parse(kSecond));
+  ASSERT_EQ(strlen(kSecond) - 3, consumed_);
+  ASSERT_EQ(RedisParser::OK, Parse("VXK\r\n*3\r\n$3\r\nSET"));
+  EXPECT_THAT(args_, ElementsAre("SET", "key:000002273458", "VXK"));
+}
+
+TEST_F(RedisParserTest, InvalidMult1) {
+  ASSERT_EQ(RedisParser::BAD_BULKLEN, Parse("*2\r\n$3\r\nFOO\r\nBAR\r\n"));
+}
+
+TEST_F(RedisParserTest, Empty) {
+  ASSERT_EQ(RedisParser::OK, Parse("*2\r\n$0\r\n\r\n$0\r\n\r\n"));
+}
+
+}  // namespace dfly
diff --git a/server/resp_expr.cc b/server/resp_expr.cc
new file mode 100644
index 0000000..b37da0b
--- /dev/null
+++ b/server/resp_expr.cc
@@ -0,0 +1,74 @@
+// Copyright 2021, Beeri 15.  All rights reserved.
+// Author: Roman Gershman (romange@gmail.com)
+//
+
+#include "server/resp_expr.h"
+
+#include "base/logging.h"
+
+namespace dfly {
+
+const char* RespExpr::TypeName(Type t) {
+  switch (t) {
+    case STRING:
+      return "string";
+    case INT64:
+      return "int";
+    case ARRAY:
+      return "array";
+    case NIL_ARRAY:
+      return "nil-array";
+    case NIL:
+      return "nil";
+    case ERROR:
+      return "error";
+  }
+  ABSL_INTERNAL_UNREACHABLE;
+}
+
+}  // namespace dfly
+
+namespace std {
+
+ostream& operator<<(ostream& os, const dfly::RespExpr& e) {
+  using dfly::RespExpr;
+  using dfly::ToAbsl;
+
+  switch (e.type) {
+    case RespExpr::INT64:
+      os << "i" << get<int64_t>(e.u);
+      break;
+    case RespExpr::STRING:
+      os << "'" << ToAbsl(get<RespExpr::Buffer>(e.u)) << "'";
+      break;
+    case RespExpr::NIL:
+      os << "nil";
+      break;
+    case RespExpr::NIL_ARRAY:
+      os << "[]";
+      break;
+    case RespExpr::ARRAY:
+      os << dfly::RespSpan{*get<RespExpr::Vec*>(e.u)};
+      break;
+    case RespExpr::ERROR:
+      os << "e(" << ToAbsl(get<RespExpr::Buffer>(e.u)) << ")";
+      break;
+  }
+
+  return os;
+}
+
+ostream& operator<<(ostream& os, dfly::RespSpan ras) {
+  os << "[";
+  if (!ras.empty()) {
+    for (size_t i = 0; i < ras.size() - 1; ++i) {
+      os << ras[i] << ",";
+    }
+    os << ras.back();
+  }
+  os << "]";
+
+  return os;
+}
+
+}  // namespace std
\ No newline at end of file
diff --git a/server/resp_expr.h b/server/resp_expr.h
new file mode 100644
index 0000000..afc95ca
--- /dev/null
+++ b/server/resp_expr.h
@@ -0,0 +1,52 @@
+// Copyright 2021, Beeri 15.  All rights reserved.
+// Author: Roman Gershman (romange@gmail.com)
+//
+
+#pragma once
+
+#include <absl/strings/ascii.h>
+#include <absl/types/span.h>
+
+#include <variant>
+#include <vector>
+
+namespace dfly {
+
+class RespExpr {
+ public:
+  using Buffer = absl::Span<uint8_t>;
+
+  enum Type : uint8_t { STRING, ARRAY, INT64, NIL, NIL_ARRAY, ERROR };
+
+  using Vec = std::vector<RespExpr>;
+  Type type;
+  bool has_support;  // whether pointers in this item are supported by external storage.
+
+  std::variant<int64_t, Buffer, Vec*> u;
+
+  RespExpr(Type t = NIL) : type(t), has_support(false) {
+  }
+
+  static Buffer buffer(std::string* s) {
+    return Buffer{reinterpret_cast<uint8_t*>(s->data()), s->size()};
+  }
+
+  Buffer GetBuf() const { return std::get<Buffer>(u); }
+
+  static const char* TypeName(Type t);
+};
+
+using RespVec = RespExpr::Vec;
+using RespSpan = absl::Span<const RespExpr>;
+
+inline std::string_view ToAbsl(const absl::Span<uint8_t>& s) {
+  return std::string_view{reinterpret_cast<char*>(s.data()), s.size()};
+}
+
+}  // namespace dfly
+
+namespace std {
+ostream& operator<<(ostream& os, const dfly::RespExpr& e);
+ostream& operator<<(ostream& os, dfly::RespSpan rspan);
+
+}  // namespace std
\ No newline at end of file
diff --git a/server/test_utils.cc b/server/test_utils.cc
new file mode 100644
index 0000000..91bc956
--- /dev/null
+++ b/server/test_utils.cc
@@ -0,0 +1,114 @@
+// Copyright 2021, Beeri 15.  All rights reserved.
+// Author: Roman Gershman (romange@gmail.com)
+//
+
+#include "server/test_utils.h"
+
+#include <absl/strings/match.h>
+
+#include "base/logging.h"
+#include "util/uring/uring_pool.h"
+
+namespace dfly {
+
+using namespace testing;
+using namespace util;
+using namespace std;
+
+bool RespMatcher::MatchAndExplain(const RespExpr& e, MatchResultListener* listener) const {
+  if (e.type != type_) {
+    *listener << "\nWrong type: " << e.type;
+    return false;
+  }
+
+  if (type_ == RespExpr::STRING || type_ == RespExpr::ERROR) {
+    RespExpr::Buffer ebuf = e.GetBuf();
+    std::string_view actual{reinterpret_cast<char*>(ebuf.data()), ebuf.size()};
+
+    if (type_ == RespExpr::ERROR && !absl::StrContains(actual, exp_str_)) {
+      *listener << "Actual does not contain '" << exp_str_ << "'";
+      return false;
+    }
+    if (type_ == RespExpr::STRING  && exp_str_ != actual) {
+      *listener << "\nActual string: " << actual;
+      return false;
+    }
+  } else if (type_ == RespExpr::INT64) {
+    auto actual = get<int64_t>(e.u);
+    if (exp_int_ != actual) {
+      *listener << "\nActual : " << actual << " expected: " << exp_int_;
+      return false;
+    }
+  } else if (type_ == RespExpr::ARRAY) {
+    size_t len = get<RespVec*>(e.u)->size();
+    if (len != size_t(exp_int_)) {
+      *listener << "Actual length " << len << ", expected: " << exp_int_;
+      return false;
+    }
+  }
+
+  return true;
+}
+
+void RespMatcher::DescribeTo(std::ostream* os) const {
+  *os << "is ";
+  switch (type_) {
+    case RespExpr::STRING:
+    case RespExpr::ERROR:
+      *os << exp_str_;
+      break;
+
+    case RespExpr::INT64:
+      *os << exp_str_;
+      break;
+    default:
+      *os << "TBD";
+      break;
+  }
+}
+
+void RespMatcher::DescribeNegationTo(std::ostream* os) const {
+  *os << "is not ";
+}
+
+bool RespTypeMatcher::MatchAndExplain(const RespExpr& e, MatchResultListener* listener) const {
+  if (e.type != type_) {
+    *listener << "\nWrong type: " << RespExpr::TypeName(e.type);
+    return false;
+  }
+
+  return true;
+}
+
+void RespTypeMatcher::DescribeTo(std::ostream* os) const {
+  *os << "is " << RespExpr::TypeName(type_);
+}
+
+void RespTypeMatcher::DescribeNegationTo(std::ostream* os) const {
+  *os << "is not " << RespExpr::TypeName(type_);
+}
+
+void PrintTo(const RespExpr::Vec& vec, std::ostream* os) {
+  *os << "Vec: [";
+  if (!vec.empty()) {
+    for (size_t i = 0; i < vec.size() - 1; ++i) {
+      *os << vec[i] << ",";
+    }
+    *os << vec.back();
+  }
+  *os << "]\n";
+}
+
+vector<int64_t> ToIntArr(const RespVec& vec) {
+  vector<int64_t> res;
+  for (auto a : vec) {
+    int64_t val;
+    std::string_view s = ToAbsl(a.GetBuf());
+    CHECK(absl::SimpleAtoi(s, &val)) << s;
+    res.push_back(val);
+  }
+
+  return res;
+}
+
+}  // namespace dfly
diff --git a/server/test_utils.h b/server/test_utils.h
new file mode 100644
index 0000000..0fa7307
--- /dev/null
+++ b/server/test_utils.h
@@ -0,0 +1,86 @@
+// Copyright 2021, Beeri 15.  All rights reserved.
+// Author: Roman Gershman (romange@gmail.com)
+//
+
+#pragma once
+
+#include <gmock/gmock.h>
+
+#include "io/io.h"
+#include "server/redis_parser.h"
+#include "util/proactor_pool.h"
+
+namespace dfly {
+
+class RespMatcher {
+ public:
+  RespMatcher(std::string_view val, RespExpr::Type t = RespExpr::STRING) : type_(t), exp_str_(val) {
+  }
+
+  RespMatcher(int64_t val, RespExpr::Type t = RespExpr::INT64)
+      : type_(t), exp_int_(val) {
+  }
+
+  using is_gtest_matcher = void;
+
+  bool MatchAndExplain(const RespExpr& e, testing::MatchResultListener*) const;
+
+  void DescribeTo(std::ostream* os) const;
+
+  void DescribeNegationTo(std::ostream* os) const;
+
+ private:
+  RespExpr::Type type_;
+
+  std::string exp_str_;
+  int64_t exp_int_;
+};
+
+class RespTypeMatcher {
+ public:
+  RespTypeMatcher(RespExpr::Type type) : type_(type) {
+  }
+
+  using is_gtest_matcher = void;
+
+  bool MatchAndExplain(const RespExpr& e, testing::MatchResultListener*) const;
+
+  void DescribeTo(std::ostream* os) const;
+
+  void DescribeNegationTo(std::ostream* os) const;
+
+ private:
+  RespExpr::Type type_;
+};
+
+inline ::testing::PolymorphicMatcher<RespMatcher> StrArg(std::string_view str) {
+  return ::testing::MakePolymorphicMatcher(RespMatcher(str));
+}
+
+inline ::testing::PolymorphicMatcher<RespMatcher> ErrArg(std::string_view str) {
+  return ::testing::MakePolymorphicMatcher(RespMatcher(str, RespExpr::ERROR));
+}
+
+inline ::testing::PolymorphicMatcher<RespMatcher> IntArg(int64_t ival) {
+  return ::testing::MakePolymorphicMatcher(RespMatcher(ival));
+}
+
+inline ::testing::PolymorphicMatcher<RespMatcher> ArrLen(size_t len) {
+  return ::testing::MakePolymorphicMatcher(RespMatcher(len, RespExpr::ARRAY));
+}
+
+inline ::testing::PolymorphicMatcher<RespTypeMatcher> ArgType(RespExpr::Type t) {
+  return ::testing::MakePolymorphicMatcher(RespTypeMatcher(t));
+}
+
+inline bool operator==(const RespExpr& left, const char* s) {
+  return left.type == RespExpr::STRING && ToAbsl(left.GetBuf()) == s;
+}
+
+void PrintTo(const RespExpr::Vec& vec, std::ostream* os);
+
+MATCHER_P(RespEq, val, "") {
+  return ::testing::ExplainMatchResult(::testing::ElementsAre(StrArg(val)), arg, result_listener);
+}
+
+}  // namespace dfly