diff --git a/src/dal/IDatabase.hpp b/src/dal/IDatabase.hpp
index dee1df5..eb49ae4 100644
--- a/src/dal/IDatabase.hpp
+++ b/src/dal/IDatabase.hpp
@@ -1,32 +1,34 @@
 #pragma once
-#include <optional>
+#include "Models.hpp"
 #include <string>
 #include <vector>
-#include "Models.hpp"
+#include <utility>
+#include <optional>
 
+namespace kom {
 class IDatabase {
 public:
-    virtual ~IDatabase() = default;
+  virtual ~IDatabase() = default;
+  // Upsert item by (namespace,key); returns {item_id, new_revision}.
+  virtual std::pair<std::string,int> upsertItem(
+      const std::string& namespace_id,
+      const std::optional<std::string>& key,
+      const std::string& content,
+      const std::string& metadata_json,
+      const std::vector<std::string>& tags) = 0;
 
-    /**
-     * Initialise the connection using a libpq/pqxx compatible DSN.
-     * The stub implementation keeps data in-process but honours the API.
-     */
-    virtual bool connect(const std::string& dsn) = 0;
-    virtual void close() = 0;
+  // Insert a chunk; returns chunk_id.
+  virtual std::string insertChunk(const std::string& item_id, int seq, const std::string& content) = 0;
 
-    // Transactions
-    virtual bool begin() = 0;
-    virtual bool commit() = 0;
-    virtual void rollback() = 0;
+  // Insert an embedding for a chunk.
+  virtual void insertEmbedding(const Embedding& e) = 0;
 
-    // Memory ops (skeleton)
-    virtual std::optional<NamespaceRow> ensureNamespace(const std::string& name) = 0;
-    virtual std::optional<NamespaceRow> findNamespace(const std::string& name) const = 0;
-    virtual std::string upsertItem(const ItemRow& item) = 0;
-    virtual std::vector<std::string> upsertChunks(const std::vector<ChunkRow>& chunks) = 0;
-    virtual std::vector<std::string> upsertEmbeddings(const std::vector<EmbeddingRow>& embs) = 0;
-    virtual std::vector<ItemRow> searchText(const std::string& namespace_id, const std::string& query, int k) = 0;
-    virtual std::vector<std::pair<std::string,float>> searchVector(const std::string& namespace_id, const std::vector<float>& embedding, int k) = 0;
-    virtual std::optional<ItemRow> getItemById(const std::string& item_id) = 0;
+  // Hybrid search. Returns chunk_ids ordered by relevance.
+  virtual std::vector<std::string> hybridSearch(
+    const std::vector<float>& query_vec,
+    const std::string& model,
+    const std::string& namespace_id,
+    const std::string& query_text,
+    int k) = 0;
 };
+}
diff --git a/src/dal/Models.hpp b/src/dal/Models.hpp
index 0f034d1..5dfcdc6 100644
--- a/src/dal/Models.hpp
+++ b/src/dal/Models.hpp
@@ -2,36 +2,30 @@
 #include <string>
 #include <vector>
 #include <optional>
-#include <unordered_map>
+#include <cstdint>
 
-struct NamespaceRow { std::string id; std::string name; };
-struct ThreadRow { std::string id; std::string namespace_id; std::string external_id; };
-struct UserRow { std::string id; std::string external_id; };
-
-struct ItemRow {
-    std::string id;
-    std::string namespace_id;
-    std::optional<std::string> thread_id;
-    std::optional<std::string> user_id;
-    std::optional<std::string> key;
-    std::string content_json;
-    std::optional<std::string> text;
-    std::vector<std::string> tags;
-    std::unordered_map<std::string, std::string> metadata;
-    int revision{1};
+namespace kom {
+struct MemoryItem {
+  std::string id;
+  std::string namespace_id;
+  std::optional<std::string> key;
+  std::string content;
+  std::string metadata_json;
+  std::vector<std::string> tags;
+  int revision = 1;
 };
 
-struct ChunkRow {
-    std::string id;
-    std::string item_id;
-    int ord{0};
-    std::string text;
+struct MemoryChunk {
+  std::string id;
+  std::string item_id;
+  int seq = 0;
+  std::string content;
 };
 
-struct EmbeddingRow {
-    std::string id;
-    std::string chunk_id;
-    std::string model;
-    int dim{0};
-    std::vector<float> vector;
+struct Embedding {
+  std::string chunk_id;
+  std::string model;
+  int dim = 1536;
+  std::vector<float> vector;
 };
+}
diff --git a/src/dal/PgDal.cpp b/src/dal/PgDal.cpp
index 1418856..f294eda 100644
--- a/src/dal/PgDal.cpp
+++ b/src/dal/PgDal.cpp
@@ -2,190 +2,303 @@
 
 #include <algorithm>
 #include <cctype>
-#include <cstddef>
-#include <mutex>
 #include <numeric>
 #include <stdexcept>
 
-bool PgDal::connect(const std::string& dsn) {
-    std::lock_guard<std::mutex> lock(guard_);
-    dsn_ = dsn;
-    connected_ = true;
-    return true;
+namespace kom {
+
+namespace {
+
+bool idsContains(const std::vector<std::string>& ids, const std::string& value) {
+  return std::find(ids.begin(), ids.end(), value) != ids.end();
 }
 
-void PgDal::close() {
-    std::lock_guard<std::mutex> lock(guard_);
-    connected_ = false;
-    inTransaction_ = false;
+} // namespace
+
+PgDal::PgDal() = default;
+PgDal::~PgDal() = default;
+
+bool PgDal::connect(const std::string& dsn) {
+  dsn_ = dsn;
+  connected_ = true;
+  useInMemory_ = true;
+
+  namespacesByName_.clear();
+  namespacesById_.clear();
+  items_.clear();
+  itemsByNamespace_.clear();
+  chunks_.clear();
+  chunksByItem_.clear();
+  embeddings_.clear();
+
+  nextNamespaceId_ = 1;
+  nextItemId_ = 1;
+  nextChunkId_ = 1;
+  nextEmbeddingId_ = 1;
+
+  return connected_;
 }
 
 bool PgDal::begin() {
-    std::lock_guard<std::mutex> lock(guard_);
-    if (!connected_ || inTransaction_) return false;
-    inTransaction_ = true;
-    return true;
+  return connected_ && !useInMemory_;
 }
 
-bool PgDal::commit() {
-    std::lock_guard<std::mutex> lock(guard_);
-    if (!connected_ || !inTransaction_) return false;
-    inTransaction_ = false;
-    return true;
-}
+void PgDal::commit() {}
 
-void PgDal::rollback() {
-    std::lock_guard<std::mutex> lock(guard_);
-    inTransaction_ = false;
-}
+void PgDal::rollback() {}
 
 std::optional<NamespaceRow> PgDal::ensureNamespace(const std::string& name) {
-    std::lock_guard<std::mutex> lock(guard_);
-    if (name.empty()) return std::nullopt;
-    auto it = namespacesByName_.find(name);
-    if (it != namespacesByName_.end()) return it->second;
+  if (!connected_) return std::nullopt;
+  auto it = namespacesByName_.find(name);
+  if (it != namespacesByName_.end()) {
+    return it->second;
+  }
 
-    NamespaceRow row;
-    row.id = makeSyntheticId("ns");
-    row.name = name;
-    namespacesByName_[name] = row;
-    namespacesById_[row.id] = row;
-    return row;
+  NamespaceRow row;
+  row.id = allocateId(nextNamespaceId_, "ns_");
+  row.name = name;
+
+  namespacesByName_[name] = row;
+  namespacesById_[row.id] = row;
+  return row;
 }
 
 std::optional<NamespaceRow> PgDal::findNamespace(const std::string& name) const {
-    std::lock_guard<std::mutex> lock(guard_);
-    auto it = namespacesByName_.find(name);
-    if (it == namespacesByName_.end()) return std::nullopt;
-    return it->second;
+  auto it = namespacesByName_.find(name);
+  if (it == namespacesByName_.end()) {
+    return std::nullopt;
+  }
+  return it->second;
 }
 
-std::string PgDal::upsertItem(const ItemRow& item) {
-    std::lock_guard<std::mutex> lock(guard_);
-    if (item.namespace_id.empty()) throw std::runtime_error("item missing namespace_id");
+std::string PgDal::upsertItem(const ItemRow& row) {
+  if (!connected_) {
+    throw std::runtime_error("PgDal not connected");
+  }
 
-    ItemRow stored = item;
-    if (stored.id.empty()) {
-        stored.id = makeSyntheticId("item");
-    }
-    itemsById_[stored.id] = stored;
+  ItemRow stored = row;
+  if (stored.id.empty()) {
+    stored.id = allocateId(nextItemId_, "item_");
+  }
 
-    auto& bucket = itemsByNamespace_[stored.namespace_id];
-    if (std::find(bucket.begin(), bucket.end(), stored.id) == bucket.end()) {
-        bucket.push_back(stored.id);
-    }
-    return stored.id;
+  auto existing = items_.find(stored.id);
+  if (existing != items_.end()) {
+    stored.revision = existing->second.revision + 1;
+  }
+
+  items_[stored.id] = stored;
+
+  auto& bucket = itemsByNamespace_[stored.namespace_id];
+  if (!idsContains(bucket, stored.id)) {
+    bucket.push_back(stored.id);
+  }
+
+  return stored.id;
 }
 
 std::vector<std::string> PgDal::upsertChunks(const std::vector<ChunkRow>& chunks) {
-    std::lock_guard<std::mutex> lock(guard_);
-    std::vector<std::string> ids;
-    ids.reserve(chunks.size());
-    for (auto chunk : chunks) {
-        if (chunk.id.empty()) {
-            chunk.id = makeSyntheticId("chunk");
-        }
-        chunksById_[chunk.id] = chunk;
-        ids.push_back(chunk.id);
+  if (!connected_) {
+    throw std::runtime_error("PgDal not connected");
+  }
+
+  std::vector<std::string> ids;
+  ids.reserve(chunks.size());
+
+  for (const auto& input : chunks) {
+    ChunkRow stored = input;
+    if (stored.item_id.empty()) {
+      continue;
     }
-    return ids;
-}
-
-std::vector<std::string> PgDal::upsertEmbeddings(const std::vector<EmbeddingRow>& embs) {
-    std::lock_guard<std::mutex> lock(guard_);
-    std::vector<std::string> ids;
-    ids.reserve(embs.size());
-    for (auto emb : embs) {
-        if (emb.id.empty()) {
-            emb.id = makeSyntheticId("emb");
-        }
-        embeddingsById_[emb.id] = emb;
-        ids.push_back(emb.id);
-    }
-    return ids;
-}
-
-std::vector<ItemRow> PgDal::searchText(const std::string& namespace_id, const std::string& query, int k) {
-    std::lock_guard<std::mutex> lock(guard_);
-    std::vector<ItemRow> result;
-    auto nsIt = itemsByNamespace_.find(namespace_id);
-    if (nsIt == itemsByNamespace_.end()) return result;
-
-    const std::string needle = toLowerCopy(query);
-    for (const auto& itemId : nsIt->second) {
-        auto itemIt = itemsById_.find(itemId);
-        if (itemIt == itemsById_.end()) continue;
-
-        if (needle.empty()) {
-            result.push_back(itemIt->second);
-        } else {
-            std::string hay = toLowerCopy(itemIt->second.text.value_or(""));
-            if (hay.find(needle) != std::string::npos) {
-                result.push_back(itemIt->second);
-            }
-        }
-
-        if (k > 0 && static_cast<int>(result.size()) >= k) break;
-    }
-    return result;
-}
-
-std::vector<std::pair<std::string, float>> PgDal::searchVector(const std::string& namespace_id, const std::vector<float>& embedding, int k) {
-    std::lock_guard<std::mutex> lock(guard_);
-    std::unordered_map<std::string, float> bestScoreByItem;
-    if (embedding.empty()) return {};
-
-    for (const auto& [embeddingId, row] : embeddingsById_) {
-        auto chunkIt = chunksById_.find(row.chunk_id);
-        if (chunkIt == chunksById_.end()) continue;
-        auto itemIt = itemsById_.find(chunkIt->second.item_id);
-        if (itemIt == itemsById_.end()) continue;
-        if (itemIt->second.namespace_id != namespace_id) continue;
-
-        const auto& storedVec = row.vector;
-        if (storedVec.empty()) continue;
-        std::size_t dim = std::min(storedVec.size(), embedding.size());
-        if (dim == 0) continue;
-
-        auto span = static_cast<std::ptrdiff_t>(dim);
-        float dot = std::inner_product(storedVec.begin(), storedVec.begin() + span,
-                                       embedding.begin(), 0.0f);
-        float score = dot / static_cast<float>(dim);
-
-        auto [it, inserted] = bestScoreByItem.emplace(itemIt->first, score);
-        if (!inserted && score > it->second) {
-            it->second = score;
-        }
+    if (stored.id.empty()) {
+      stored.id = allocateId(nextChunkId_, "chunk_");
     }
 
-    std::vector<std::pair<std::string, float>> scored;
-    scored.reserve(bestScoreByItem.size());
-    for (const auto& kv : bestScoreByItem) scored.push_back(kv);
-
-    std::sort(scored.begin(), scored.end(), [](const auto& lhs, const auto& rhs) {
-        return lhs.second > rhs.second;
-    });
-    if (k > 0 && static_cast<std::size_t>(k) < scored.size()) {
-        scored.resize(static_cast<std::size_t>(k));
+    chunks_[stored.id] = stored;
+    auto& bucket = chunksByItem_[stored.item_id];
+    if (!idsContains(bucket, stored.id)) {
+      bucket.push_back(stored.id);
     }
-    return scored;
+    ids.push_back(stored.id);
+  }
+
+  return ids;
 }
 
-std::optional<ItemRow> PgDal::getItemById(const std::string& item_id) {
-    std::lock_guard<std::mutex> lock(guard_);
-    auto it = itemsById_.find(item_id);
-    if (it == itemsById_.end()) return std::nullopt;
-    return it->second;
+void PgDal::upsertEmbeddings(const std::vector<EmbeddingRow>& embeddings) {
+  if (!connected_) {
+    throw std::runtime_error("PgDal not connected");
+  }
+
+  for (const auto& input : embeddings) {
+    if (input.chunk_id.empty()) {
+      continue;
+    }
+    EmbeddingRow stored = input;
+    if (stored.id.empty()) {
+      stored.id = allocateId(nextEmbeddingId_, "emb_");
+    }
+    embeddings_[stored.chunk_id] = stored;
+  }
 }
 
-std::string PgDal::makeSyntheticId(const std::string& prefix) {
-    return prefix + "-" + std::to_string(idCounter_++);
+std::vector<ItemRow> PgDal::searchText(const std::string& namespaceId,
+                                       const std::string& query,
+                                       int limit) {
+  std::vector<ItemRow> results;
+  if (!connected_) return results;
+  auto bucketIt = itemsByNamespace_.find(namespaceId);
+  if (bucketIt == itemsByNamespace_.end()) return results;
+
+  const std::string loweredQuery = toLower(query);
+
+  for (const auto& itemId : bucketIt->second) {
+    auto itemIt = items_.find(itemId);
+    if (itemIt == items_.end()) continue;
+
+    if (!loweredQuery.empty()) {
+      const std::string loweredText = toLower(itemIt->second.text.value_or(std::string()));
+      if (loweredText.find(loweredQuery) == std::string::npos) {
+        continue;
+      }
+    }
+
+    results.push_back(itemIt->second);
+    if (static_cast<int>(results.size()) >= limit) break;
+  }
+
+  return results;
 }
 
-std::string PgDal::toLowerCopy(const std::string& in) {
-    std::string out = in;
-    std::transform(out.begin(), out.end(), out.begin(), [](unsigned char c) {
-        return static_cast<char>(std::tolower(c));
-    });
-    return out;
+std::vector<std::pair<std::string, float>> PgDal::searchVector(
+    const std::string& namespaceId,
+    const std::vector<float>& embedding,
+    int limit) {
+  std::vector<std::pair<std::string, float>> scores;
+  if (!connected_ || embedding.empty()) return scores;
+
+  auto bucketIt = itemsByNamespace_.find(namespaceId);
+  if (bucketIt == itemsByNamespace_.end()) return scores;
+
+  for (const auto& itemId : bucketIt->second) {
+    auto chunkBucketIt = chunksByItem_.find(itemId);
+    if (chunkBucketIt == chunksByItem_.end()) continue;
+
+    float bestScore = -1.0f;
+    for (const auto& chunkId : chunkBucketIt->second) {
+      auto embIt = embeddings_.find(chunkId);
+      if (embIt == embeddings_.end()) continue;
+      const auto& storedVec = embIt->second.vector;
+      if (storedVec.size() != embedding.size() || storedVec.empty()) continue;
+      float dot = std::inner_product(storedVec.begin(), storedVec.end(), embedding.begin(), 0.0f);
+      if (dot > bestScore) {
+        bestScore = dot;
+      }
+    }
+
+    if (bestScore >= 0.0f) {
+      scores.emplace_back(itemId, bestScore);
+    }
+  }
+
+  std::sort(scores.begin(), scores.end(),
+            [](const auto& lhs, const auto& rhs) {
+              if (lhs.second == rhs.second) {
+                return lhs.first < rhs.first;
+              }
+              return lhs.second > rhs.second;
+            });
+
+  if (static_cast<int>(scores.size()) > limit) {
+    scores.resize(static_cast<std::size_t>(limit));
+  }
+
+  return scores;
 }
+
+std::optional<ItemRow> PgDal::getItemById(const std::string& id) const {
+  auto it = items_.find(id);
+  if (it == items_.end()) {
+    return std::nullopt;
+  }
+  return it->second;
+}
+
+std::pair<std::string, int> PgDal::upsertItem(
+    const std::string& namespace_id,
+    const std::optional<std::string>& key,
+    const std::string& content,
+    const std::string& metadata_json,
+    const std::vector<std::string>& tags) {
+  ItemRow row;
+  row.namespace_id = namespace_id;
+  row.key = key;
+  row.content_json = metadata_json.empty() ? content : metadata_json;
+  if (!content.empty()) {
+    row.text = content;
+  }
+  row.tags = tags;
+  const std::string id = upsertItem(row);
+  const auto stored = items_.find(id);
+  const int revision = stored != items_.end() ? stored->second.revision : 1;
+  return {id, revision};
+}
+
+std::string PgDal::insertChunk(const std::string& item_id,
+                               int seq,
+                               const std::string& content) {
+  ChunkRow row;
+  row.item_id = item_id;
+  row.ord = seq;
+  row.text = content;
+  auto ids = upsertChunks(std::vector<ChunkRow>{row});
+  return ids.empty() ? std::string() : ids.front();
+}
+
+void PgDal::insertEmbedding(const Embedding& embedding) {
+  EmbeddingRow row;
+  row.chunk_id = embedding.chunk_id;
+  row.model = embedding.model;
+  row.dim = embedding.dim;
+  row.vector = embedding.vector;
+  upsertEmbeddings(std::vector<EmbeddingRow>{row});
+}
+
+std::vector<std::string> PgDal::hybridSearch(const std::vector<float>& query_vec,
+                                             const std::string& model,
+                                             const std::string& namespace_id,
+                                             const std::string& query_text,
+                                             int k) {
+  (void)model;
+
+  std::vector<std::string> results;
+  auto textMatches = searchText(namespace_id, query_text, k);
+  for (const auto& item : textMatches) {
+    results.push_back(item.id);
+    if (static_cast<int>(results.size()) >= k) {
+      return results;
+    }
+  }
+
+  auto vectorMatches = searchVector(namespace_id, query_vec, k);
+  for (const auto& pair : vectorMatches) {
+    if (!idsContains(results, pair.first)) {
+      results.push_back(pair.first);
+    }
+    if (static_cast<int>(results.size()) >= k) break;
+  }
+
+  return results;
+}
+
+std::string PgDal::allocateId(std::size_t& counter, const std::string& prefix) {
+  return prefix + std::to_string(counter++);
+}
+
+std::string PgDal::toLower(const std::string& value) {
+  std::string lowered = value;
+  std::transform(lowered.begin(), lowered.end(), lowered.begin(),
+                 [](unsigned char c) { return static_cast<char>(std::tolower(c)); });
+  return lowered;
+}
+
+} // namespace kom
diff --git a/src/dal/PgDal.hpp b/src/dal/PgDal.hpp
index c37e88b..5e1aebc 100644
--- a/src/dal/PgDal.hpp
+++ b/src/dal/PgDal.hpp
@@ -1,42 +1,107 @@
 #pragma once
+
 #include "IDatabase.hpp"
-#include <mutex>
+
+#include <optional>
 #include <string>
 #include <unordered_map>
 #include <vector>
 
-class PgDal : public IDatabase {
-public:
-    bool connect(const std::string& dsn) override;
-    void close() override;
-    bool begin() override;
-    bool commit() override;
-    void rollback() override;
+namespace kom {
 
-    std::optional<NamespaceRow> ensureNamespace(const std::string& name) override;
-    std::optional<NamespaceRow> findNamespace(const std::string& name) const override;
-    std::string upsertItem(const ItemRow& item) override;
-    std::vector<std::string> upsertChunks(const std::vector<ChunkRow>& chunks) override;
-    std::vector<std::string> upsertEmbeddings(const std::vector<EmbeddingRow>& embs) override;
-    std::vector<ItemRow> searchText(const std::string& namespace_id, const std::string& query, int k) override;
-    std::vector<std::pair<std::string,float>> searchVector(const std::string& namespace_id, const std::vector<float>& embedding, int k) override;
-    std::optional<ItemRow> getItemById(const std::string& item_id) override;
+struct NamespaceRow {
+  std::string id;
+  std::string name;
+};
+
+struct ItemRow {
+  std::string id;
+  std::string namespace_id;
+  std::optional<std::string> key;
+  std::string content_json;
+  std::optional<std::string> text;
+  std::vector<std::string> tags;
+  int revision = 1;
+};
+
+struct ChunkRow {
+  std::string id;
+  std::string item_id;
+  int ord = 0;
+  std::string text;
+};
+
+struct EmbeddingRow {
+  std::string id;
+  std::string chunk_id;
+  std::string model;
+  int dim = 0;
+  std::vector<float> vector;
+};
+
+class PgDal final : public IDatabase {
+public:
+  PgDal();
+  ~PgDal();
+
+  bool connect(const std::string& dsn);
+  bool begin();
+  void commit();
+  void rollback();
+
+  std::optional<NamespaceRow> ensureNamespace(const std::string& name);
+  std::optional<NamespaceRow> findNamespace(const std::string& name) const;
+
+  std::string upsertItem(const ItemRow& row);
+  std::vector<std::string> upsertChunks(const std::vector<ChunkRow>& chunks);
+  void upsertEmbeddings(const std::vector<EmbeddingRow>& embeddings);
+
+  std::vector<ItemRow> searchText(const std::string& namespaceId,
+                                  const std::string& query,
+                                  int limit);
+  std::vector<std::pair<std::string, float>> searchVector(
+      const std::string& namespaceId,
+      const std::vector<float>& embedding,
+      int limit);
+  std::optional<ItemRow> getItemById(const std::string& id) const;
+
+  // IDatabase overrides (stubbed for now to operate on the in-memory backing store).
+  std::pair<std::string, int> upsertItem(
+      const std::string& namespace_id,
+      const std::optional<std::string>& key,
+      const std::string& content,
+      const std::string& metadata_json,
+      const std::vector<std::string>& tags) override;
+  std::string insertChunk(const std::string& item_id,
+                          int seq,
+                          const std::string& content) override;
+  void insertEmbedding(const Embedding& embedding) override;
+  std::vector<std::string> hybridSearch(const std::vector<float>& query_vec,
+                                        const std::string& model,
+                                        const std::string& namespace_id,
+                                        const std::string& query_text,
+                                        int k) override;
 
 private:
-    std::string makeSyntheticId(const std::string& prefix);
-    static std::string toLowerCopy(const std::string& in);
+  std::string allocateId(std::size_t& counter, const std::string& prefix);
+  static std::string toLower(const std::string& value);
 
-    bool connected_{false};
-    bool inTransaction_{false};
-    std::string dsn_;
-    std::size_t idCounter_{1};
+  bool connected_ = false;
+  bool useInMemory_ = true;
+  std::string dsn_;
 
-    std::unordered_map<std::string, NamespaceRow> namespacesByName_;
-    std::unordered_map<std::string, NamespaceRow> namespacesById_;
-    std::unordered_map<std::string, ItemRow> itemsById_;
-    std::unordered_map<std::string, std::vector<std::string>> itemsByNamespace_;
-    std::unordered_map<std::string, ChunkRow> chunksById_;
-    std::unordered_map<std::string, EmbeddingRow> embeddingsById_;
+  std::size_t nextNamespaceId_ = 1;
+  std::size_t nextItemId_ = 1;
+  std::size_t nextChunkId_ = 1;
+  std::size_t nextEmbeddingId_ = 1;
 
-    mutable std::mutex guard_;
+  std::unordered_map<std::string, NamespaceRow> namespacesByName_;
+  std::unordered_map<std::string, NamespaceRow> namespacesById_;
+  std::unordered_map<std::string, ItemRow> items_;
+  std::unordered_map<std::string, std::vector<std::string>> itemsByNamespace_;
+  std::unordered_map<std::string, ChunkRow> chunks_;
+  std::unordered_map<std::string, std::vector<std::string>> chunksByItem_;
+  std::unordered_map<std::string, EmbeddingRow> embeddings_;
 };
+
+} // namespace kom
diff --git a/src/mcp/HandlersMemory.hpp b/src/mcp/HandlersMemory.hpp
index 56fc7ae..02e88bb 100644
--- a/src/mcp/HandlersMemory.hpp
+++ b/src/mcp/HandlersMemory.hpp
@@ -15,8 +15,8 @@
 namespace Handlers {
 namespace detail {
 
-inline PgDal& database() {
-    static PgDal instance;
+inline kom::PgDal& database() {
+    static kom::PgDal instance;
     static bool connected = [] {
         const char* env = std::getenv("PG_DSN");
         const std::string dsn = (env && *env) ? std::string(env) : std::string();
@@ -321,14 +321,14 @@ inline std::string upsert_memory(const std::string& reqJson) {
         return detail::error_response("bad_request", "items array must contain at least one entry");
     }
 
-    PgDal& dal = detail::database();
+    kom::PgDal& dal = detail::database();
     const bool hasTx = dal.begin();
     std::vector<std::string> ids;
     ids.reserve(items.size());
 
     try {
         for (auto& parsed : items) {
-            ItemRow row;
+            kom::ItemRow row;
             row.id = parsed.id;
             row.namespace_id = nsRow->id;
             row.content_json = parsed.rawJson;
@@ -340,18 +340,18 @@ inline std::string upsert_memory(const std::string& reqJson) {
             ids.push_back(itemId);
 
             if (!parsed.embedding.empty()) {
-                ChunkRow chunk;
+                kom::ChunkRow chunk;
                 chunk.item_id = itemId;
                 chunk.ord = 0;
                 chunk.text = parsed.text;
-                auto chunkIds = dal.upsertChunks({chunk});
+                auto chunkIds = dal.upsertChunks(std::vector<kom::ChunkRow>{chunk});
 
-                EmbeddingRow emb;
+                kom::EmbeddingRow emb;
                 emb.chunk_id = chunkIds.front();
                 emb.model = "stub-model";
                 emb.dim = static_cast<int>(parsed.embedding.size());
                 emb.vector = parsed.embedding;
-                dal.upsertEmbeddings({emb});
+                dal.upsertEmbeddings(std::vector<kom::EmbeddingRow>{emb});
             }
         }
         if (hasTx) dal.commit();
@@ -397,7 +397,7 @@ inline std::string search_memory(const std::string& reqJson) {
         }
     }
 
-    PgDal& dal = detail::database();
+    kom::PgDal& dal = detail::database();
     std::unordered_set<std::string> seen;
     std::vector<detail::SearchMatch> matches;