diff --git a/ecsact/entt/detail/id_map.hh b/ecsact/entt/detail/id_map.hh
new file mode 100644
index 0000000..b518c4f
--- /dev/null
+++ b/ecsact/entt/detail/id_map.hh
@@ -0,0 +1,48 @@
+#pragma once
+
+#include <type_traits>
+#include <concepts>
+#include <array>
+
+namespace ecsact::entt::detail {
+
+/**
+ *
+ */
+template<typename KeyT, typename ValueT, KeyT MinKeyValue, KeyT MaxKeyValue>
+class id_map {
+public:
+	using key_type = KeyT;
+	using value_type = ValueT;
+	using underlying_key_type = std::underlying_type_t<key_type>;
+
+	static constexpr auto min_key_value() -> underlying_key_type {
+		return static_cast<underlying_key_type>(MinKeyValue);
+	}
+
+	static constexpr auto max_key_value() -> underlying_key_type {
+		return static_cast<underlying_key_type>(MaxKeyValue);
+	}
+
+	static_assert(
+		max_key_value() > min_key_value(),
+		"id_map MaxKeyValue must be > MinKeyValue"
+	);
+
+	std::array<ValueT, max_key_value() - min_key_value()> _data;
+
+	constexpr auto key_index(const key_type& key) const -> size_t {
+		auto index = static_cast<size_t>(key);
+		index -= static_cast<size_t>(min_key_value());
+		return index;
+	}
+
+	constexpr auto operator[](const key_type& key) -> value_type& {
+		return _data[key_index(key)];
+	}
+
+	constexpr auto operator[](const key_type& key) const -> const value_type& {
+		return _data[key_index(key)];
+	}
+};
+} // namespace ecsact::entt::detail
diff --git a/rt_entt_codegen/core/execution_options.cc b/rt_entt_codegen/core/execution_options.cc
index 5a16d1c..c6bb1ca 100644
--- a/rt_entt_codegen/core/execution_options.cc
+++ b/rt_entt_codegen/core/execution_options.cc
@@ -37,7 +37,7 @@ inline auto print_static_maps(
 
 	block(
 		ctx,
-		"static const auto execution_update_fns="
+		"static const auto execution_update_fns ="
 		"std::unordered_map<ecsact_component_like_id, "
 		"decltype(&ecsact_update_component)>\n",
 		[&] {
diff --git a/rt_entt_codegen/core/system_provider/system_ctx_functions.cc b/rt_entt_codegen/core/system_provider/system_ctx_functions.cc
index 8715a25..1d91f18 100644
--- a/rt_entt_codegen/core/system_provider/system_ctx_functions.cc
+++ b/rt_entt_codegen/core/system_provider/system_ctx_functions.cc
@@ -9,6 +9,7 @@ using ecsact::cc_lang_support::cpp_identifier;
 using ecsact::cpp_codegen_plugin_util::block;
 using ecsact::meta::decl_full_name;
 using ecsact::rt_entt_codegen::util::is_transient_component;
+using ecsact::rt_entt_codegen::util::make_id_map_type;
 
 auto ecsact::rt_entt_codegen::core::provider::context_action_impl(
 	ecsact::codegen_plugin_context& ctx,
@@ -225,9 +226,9 @@ auto ecsact::rt_entt_codegen::core::provider::context_get_impl(
 	ctx.write("static const auto get_fns = []()\n");
 
 	block(ctx, "", [&] {
-		ctx.write(
-			"auto result = std::unordered_map<ecsact_component_like_id, "
-			"get_fn_t>{};\n"
+		ctx.writef(
+			"auto result = {}{{}};\n",
+			make_id_map_type<ecsact_component_like_id>("get_fn_t")
 		);
 		for(const auto comp_id : details.readable_comps) {
 			auto type_name = cpp_identifier(decl_full_name(comp_id));
@@ -245,8 +246,8 @@ auto ecsact::rt_entt_codegen::core::provider::context_get_impl(
 	ctx.write("();\n");
 
 	ctx.write(
-		"get_fns.at("
-		"component_id)(this, component_id, out_component_data, nullptr, *view"
+		"get_fns[component_id]"
+		"(this, component_id, out_component_data, nullptr, *view"
 		");\n"
 	);
 }
@@ -295,9 +296,9 @@ auto ecsact::rt_entt_codegen::core::provider::context_update_impl(
 	ctx.write("static const auto update_fns = []()\n");
 
 	block(ctx, "", [&] {
-		ctx.write(
-			"auto result = std::unordered_map<ecsact_component_like_id, "
-			"update_fn_t>{};\n"
+		ctx.writef(
+			"auto result = {}{{}};\n",
+			make_id_map_type<ecsact_component_like_id>("update_fn_t")
 		);
 		for(const auto comp_id : details.writable_comps) {
 			auto type_name = cpp_identifier(decl_full_name(comp_id));
@@ -315,8 +316,8 @@ auto ecsact::rt_entt_codegen::core::provider::context_update_impl(
 	ctx.write("();\n");
 
 	ctx.write(
-		"update_fns.at(component_id)(this, component_id, component_data, nullptr, "
-		"*view);\n"
+		"update_fns[component_id]"
+		"(this, component_id, component_data, nullptr, *view);\n"
 	);
 }
 
diff --git a/rt_entt_codegen/rt_entt_codegen.cc b/rt_entt_codegen/rt_entt_codegen.cc
index fd677de..7bdb1c1 100644
--- a/rt_entt_codegen/rt_entt_codegen.cc
+++ b/rt_entt_codegen/rt_entt_codegen.cc
@@ -138,6 +138,7 @@ void ecsact_codegen_plugin(
 	inc_header(ctx, "ecsact/entt/wrapper/core.hh");
 	inc_header(ctx, "ecsact/entt/wrapper/dynamic.hh");
 	inc_header(ctx, "ecsact/entt/error_check.hh");
+	inc_header(ctx, "ecsact/entt/detail/id_map.hh");
 	inc_header(ctx, "xxhash.h");
 	ctx.write("#include <execution>\n");
 
diff --git a/rt_entt_codegen/shared/BUILD.bazel b/rt_entt_codegen/shared/BUILD.bazel
index 0147e6b..52b0481 100644
--- a/rt_entt_codegen/shared/BUILD.bazel
+++ b/rt_entt_codegen/shared/BUILD.bazel
@@ -31,6 +31,7 @@ cc_library(
 
 cc_library(
     name = "util",
+    srcs = ["util.cc"],
     hdrs = ["util.hh"],
     copts = copts,
     defines = ["ECSACT_META_API_LOAD_AT_RUNTIME"],
diff --git a/rt_entt_codegen/shared/util.cc b/rt_entt_codegen/shared/util.cc
new file mode 100644
index 0000000..c5c7435
--- /dev/null
+++ b/rt_entt_codegen/shared/util.cc
@@ -0,0 +1,107 @@
+#include "rt_entt_codegen/shared/util.hh"
+
+#include <unordered_set>
+#include <algorithm>
+#include "ecsact/runtime/meta.hh"
+
+static auto collect_pkg_deps(
+	ecsact_package_id                      pkg_id,
+	std::unordered_set<ecsact_package_id>& out_set
+) -> void {
+	auto deps = ecsact::meta::get_dependencies(pkg_id);
+	for(auto dep : deps) {
+		if(out_set.contains(dep)) {
+			continue;
+		}
+		out_set.insert(dep);
+		collect_pkg_deps(dep, out_set);
+	}
+}
+
+static auto all_pkg_ids() -> std::unordered_set<ecsact_package_id> {
+	auto ids = std::unordered_set<ecsact_package_id>{};
+	auto main_pkg_id = ecsact::meta::main_package();
+	ids.insert(*main_pkg_id);
+	collect_pkg_deps(*main_pkg_id, ids);
+	return ids;
+}
+
+template<typename ID>
+constexpr auto default_id_min() -> ID {
+	return static_cast<ID>(std::numeric_limits<std::underlying_type_t<ID>>::max()
+	);
+}
+
+template<typename ID>
+constexpr auto default_id_max() -> ID {
+	return static_cast<ID>(std::numeric_limits<std::underlying_type_t<ID>>::min()
+	);
+}
+
+template<>
+auto ecsact::rt_entt_codegen::util::ecsact_id_min_max<ecsact_component_id>()
+	-> std::tuple<ecsact_component_id, ecsact_component_id> {
+	auto min = default_id_min<ecsact_component_id>();
+	auto max = default_id_max<ecsact_component_id>();
+	for(auto pkg_id : all_pkg_ids()) {
+		auto comp_ids = ecsact::meta::get_component_ids(pkg_id);
+		for(auto comp_id : comp_ids) {
+			if(static_cast<int>(comp_id) < static_cast<int>(min)) {
+				min = comp_id;
+			}
+
+			if(static_cast<int>(comp_id) > static_cast<int>(max)) {
+				max = comp_id;
+			}
+		}
+	}
+
+	if(min == default_id_min<ecsact_component_id>()) {
+		return {};
+	}
+
+	return {min, max};
+}
+
+template<>
+auto ecsact::rt_entt_codegen::util::ecsact_id_min_max<ecsact_transient_id>()
+	-> std::tuple<ecsact_transient_id, ecsact_transient_id> {
+	auto min = default_id_min<ecsact_transient_id>();
+	auto max = default_id_max<ecsact_transient_id>();
+	for(auto pkg_id : all_pkg_ids()) {
+		auto trans_ids = ecsact::meta::get_transient_ids(pkg_id);
+		for(auto trans_id : trans_ids) {
+			if(static_cast<int>(trans_id) < static_cast<int>(min)) {
+				min = trans_id;
+			}
+
+			if(static_cast<int>(trans_id) > static_cast<int>(max)) {
+				max = trans_id;
+			}
+		}
+	}
+
+	if(min == default_id_min<ecsact_transient_id>()) {
+		return {};
+	}
+
+	return {min, max};
+}
+
+template<>
+auto ecsact::rt_entt_codegen::util::ecsact_id_min_max<ecsact_component_like_id>(
+) -> std::tuple<ecsact_component_like_id, ecsact_component_like_id> {
+	auto [transient_min, transient_max] =
+		ecsact_id_min_max<ecsact_transient_id>();
+	auto [component_min, component_max] =
+		ecsact_id_min_max<ecsact_component_id>();
+
+	return {
+		static_cast<ecsact_component_like_id>(
+			std::min(static_cast<int>(transient_min), static_cast<int>(component_min))
+		),
+		static_cast<ecsact_component_like_id>(
+			std::max(static_cast<int>(transient_max), static_cast<int>(component_max))
+		)
+	};
+}
diff --git a/rt_entt_codegen/shared/util.hh b/rt_entt_codegen/shared/util.hh
index 02f22fe..bc5b80d 100644
--- a/rt_entt_codegen/shared/util.hh
+++ b/rt_entt_codegen/shared/util.hh
@@ -326,4 +326,49 @@ auto make_view( //
 	ctx.write(");\n");
 }
 
+template<typename ID>
+constexpr auto ecsact_id_type_to_string() -> std::string_view;
+
+template<>
+constexpr auto ecsact_id_type_to_string<ecsact_component_like_id>()
+	-> std::string_view {
+	return "ecsact_component_like_id";
+}
+
+/**
+ * Get the smallest and largest ID by number.
+ * Used when creating and id_map
+ */
+template<typename ID>
+auto ecsact_id_min_max() -> std::tuple<ID, ID>;
+
+template<>
+auto ecsact_id_min_max<ecsact_component_id>()
+	-> std::tuple<ecsact_component_id, ecsact_component_id>;
+
+template<>
+auto ecsact_id_min_max<ecsact_transient_id>()
+	-> std::tuple<ecsact_transient_id, ecsact_transient_id>;
+
+template<>
+auto ecsact_id_min_max<ecsact_component_like_id>()
+	-> std::tuple<ecsact_component_like_id, ecsact_component_like_id>;
+
+/**
+ * Helper function for printing an ecsact::entt::detail::id_map in codegen
+ */
+template<typename ID>
+auto make_id_map_type(std::string value_type) -> std::string {
+	auto id_type_str = ecsact_id_type_to_string<ID>();
+	auto [min, max] = ecsact_id_min_max<ID>();
+	return std::format(
+		"::ecsact::entt::detail::id_map<{0}, {1}, "
+		"static_cast<{0}>({2}), "
+		"static_cast<{0}>({3})>",
+		id_type_str,
+		value_type,
+		static_cast<int>(min),
+		static_cast<int>(max)
+	);
+}
 } // namespace ecsact::rt_entt_codegen::util