diff --git a/zecsy.hpp b/zecsy.hpp
index 4c2279c..325a78f 100644
--- a/zecsy.hpp
+++ b/zecsy.hpp
@@ -29,12 +29,6 @@ namespace zecsy
         return true;
     }();
 
-    /*
-     * Using std::set for entities_set to maintain sorted order, which can
-     * improve cache locality during queries and iterations.
-     */
-    using entities_set = std::set<entity_id>;
-
     class system_scheduler final
     {
     public:
@@ -120,10 +114,10 @@ namespace zecsy
         void query(std::invocable<T&...> auto&& system);
 
     private:
-        entities_set alive_entities;
-        entity_id entity_counter = 0;
-
         using comp_id = size_t;
+        std::set<entity_id> alive_entities;
+        std::unordered_map<entity_id, std::set<comp_id>> entity_to_comps;
+        entity_id entity_counter = 0;
 
         struct component_pool
         {
@@ -151,12 +145,24 @@ namespace zecsy
     {
         auto id = ++entity_counter;
         alive_entities.emplace(id);
+        // entity_to_comps[id] = {};
         return id;
     }
 
     inline void world::destroy_entity(entity_id e)
     {
         alive_entities.erase(e);
+
+        for(comp_id id: entity_to_comps[e])
+        {
+            auto& pool = pools[id];
+            auto index = pool.entity_to_index[e];
+            pool.entity_to_index.erase(e);
+            pool.index_to_entity.erase(index);
+            pool.free_list.emplace_back(index);
+        }
+
+        entity_to_comps.erase(e);
     }
 
     inline bool world::is_alive(entity_id e) const
@@ -167,10 +173,9 @@ namespace zecsy
     template<Component T>
     inline bool world::has(entity_id e) const
     {
-        auto id = get_component_id<T>();
-        if(pools.contains(id))
+        if(entity_to_comps.contains(e))
         {
-            return pools.at(id).entity_to_index.contains(e);
+            return entity_to_comps.at(e).contains(get_component_id<T>());
         }
         return false;
     }
@@ -211,6 +216,8 @@ namespace zecsy
         new(&pool.data[index * sizeof(T)]) T(comp);
         pool.entity_to_index[e] = index;
         pool.index_to_entity[index] = e;
+
+        entity_to_comps[e].emplace(id);
     }
 
     template<Component T>
@@ -234,6 +241,7 @@ namespace zecsy
         pool.free_list.push_back(index);
         pool.entity_to_index.erase(e);
         pool.index_to_entity.erase(index);
+        entity_to_comps[e].erase(id);
     }
 
     template<Component First, Component Second, Component... Rest>