diff --git a/src/core/group/group.h b/src/core/group/group.h
index 84e2c75..c6dc163 100644
--- a/src/core/group/group.h
+++ b/src/core/group/group.h
@@ -201,13 +201,14 @@ public:
 class GroupCases {
 public:
     // TODO: rename as Info and changed as class
-    struct info_t {
+    class Info {
+    public:
         uint16_t type_id;
         uint16_t group_id;
         uint32_t case_id;
 
 #ifndef KLSK_NDEBUG
-        friend std::ostream& operator<<(std::ostream &out, info_t self) {
+        friend std::ostream& operator<<(std::ostream &out, Info self) {
             out << std::format("{}-{}-{}", self.type_id, self.group_id, self.case_id);
             return out;
         }
@@ -219,24 +220,24 @@ public:
     // ------------------------------------------------------------------------------------- //
 
     /// Execute the build process.
-    void build();
+    static void build();
 
     /// Execute the build process without blocking.
-    void build_async(Executor &&executor, Notifier &&callback);
+    static void build_async(Executor &&executor, Notifier &&callback);
 
     // ------------------------------------------------------------------------------------- //
 
     /// Parse CommonCode from group info.
-    codec::CommonCode parse(info_t info);
+    // codec::CommonCode parse(Info info);
 
     /// Get group info from RawCode.
-    info_t group_info(codec::RawCode raw_code);
+    // Info get_info(codec::RawCode raw_code);
 
     /// Get group info from short code.
-    info_t group_info(codec::ShortCode short_code);
+    // Info get_info(codec::ShortCode short_code);
 
     /// Get group info from common code.
-    info_t group_info(codec::CommonCode common_code);
+    // Info get_info(codec::CommonCode common_code);
 
     // ------------------------------------------------------------------------------------- //
 
@@ -247,13 +248,26 @@ private:
     KLSK_INSTANCE(GroupCases)
 
 public:
-    // fast api
-    static info_t to_info_t(codec::ShortCode short_code);
-    static codec::CommonCode from_info_t(info_t info);
+    // ------------------------------------------------------------------------------------- //
+
+    /// Parse group info into CommonCode.
+    static codec::CommonCode tiny_parse(Info info);
+
+    /// Obtain group info from CommonCode.
+    static Info tiny_obtain(codec::CommonCode common_code);
+
+    // ------------------------------------------------------------------------------------- //
+
+    /// Quickly parse group info into CommonCode.
+    static codec::CommonCode fast_parse(Info info);
 
-    // TODO: add to_info_t(CommonCode) interface
+    /// Quickly obtain group info from ShortCode.
+    static Info fast_obtain(codec::ShortCode short_code);
 
-    // TODO: tiny api
+    /// Quickly obtain group info from CommonCode.
+    static Info fast_obtain(codec::CommonCode common_code);
+
+    // ------------------------------------------------------------------------------------- //
 };
 
 } // namespace klotski::cases
diff --git a/src/core/group/internal/group_cases.cc b/src/core/group/internal/group_cases.cc
index 76f7403..f4dbb24 100644
--- a/src/core/group/internal/group_cases.cc
+++ b/src/core/group/internal/group_cases.cc
@@ -3,20 +3,15 @@
 
 #include "group/group.h"
 
-using klotski::cases::GroupCases;
-
 using klotski::codec::ShortCode;
-
 using klotski::codec::CommonCode;
 
-using klotski::cases::RangesUnion;
-
+using klotski::cases::GroupCases;
 using klotski::cases::GroupUnion;
+using klotski::cases::RangesUnion;
 
 using klotski::cases::ALL_GROUP_NUM;
-
 using klotski::cases::TYPE_ID_LIMIT;
-
 using klotski::cases::ALL_CASES_NUM_;
 
 struct tmp_t {
@@ -28,8 +23,10 @@ static_assert(sizeof(tmp_t) == 4);
 
 // TODO: we need multi-thread support (Executor)
 
-std::vector<RangesUnion> build_ranges_unions() {
+static std::vector<tmp_t> *rev_data = nullptr;
+static std::vector<RangesUnion> *ru_data = nullptr;
 
+std::vector<RangesUnion> build_ranges_unions() {
     std::vector<RangesUnion> unions;
     unions.reserve(ALL_GROUP_NUM);
 
@@ -41,37 +38,10 @@ std::vector<RangesUnion> build_ranges_unions() {
             unions.emplace_back(group.cases());
         }
     }
-
     return unions;
 }
 
-CommonCode GroupCases::from_info_t(info_t info) {
-
-    // TODO: build as static class member (ptr)
-    static std::vector<RangesUnion> data = build_ranges_unions();
-
-    auto flat_id = GROUP_OFFSET[info.type_id] + info.group_id;
-
-    auto &cases = data[flat_id];
-    // TODO: make offset table for perf
-
-    uint64_t head = 0;
-
-    for (;;) {
-        if (info.case_id >= cases[head].size()) {
-            info.case_id -= cases[head].size();
-            ++head;
-        } else {
-            break;
-        }
-    }
-
-    auto range = cases[head][info.case_id];
-    return CommonCode::unsafe_create(head << 32 | range);
-}
-
 static std::vector<tmp_t> build_tmp_data() {
-
     std::vector<tmp_t> data;
     data.resize(ALL_CASES_NUM_);
     ShortCode::speed_up(true);
@@ -89,27 +59,68 @@ static std::vector<tmp_t> build_tmp_data() {
                     .group_id = group_id,
                     .case_id = case_id,
                 };
-
             }
         }
     }
-
     return data;
+}
 
+void GroupCases::build() {
+    static auto data_1 = build_ranges_unions();
+    static auto data_2 = build_tmp_data();
+    ru_data = &data_1;
+    rev_data = &data_2;
 }
 
-GroupCases::info_t GroupCases::to_info_t(codec::ShortCode short_code) {
+CommonCode GroupCases::fast_parse(Info info) {
+
+    auto flat_id = GROUP_OFFSET[info.type_id] + info.group_id;
+
+    auto &cases = (*ru_data)[flat_id];
+    // TODO: make offset table for perf
+
+    uint64_t head = 0;
+
+    for (;;) {
+        if (info.case_id >= cases[head].size()) {
+            info.case_id -= cases[head].size();
+            ++head;
+        } else {
+            break;
+        }
+    }
+
+    auto range = cases[head][info.case_id];
+    return CommonCode::unsafe_create(head << 32 | range);
+}
 
-    // TODO: build as static class member (ptr)
-    static auto data = build_tmp_data();
+GroupCases::Info GroupCases::fast_obtain(codec::ShortCode short_code) {
 
     uint16_t type_id = GroupUnion::from_short_code(short_code).unwrap(); // NOTE: need to convert as CommonCode
-    uint16_t group_id = data[short_code.unwrap()].group_id;
-    auto case_id = data[short_code.unwrap()].case_id;
+    uint16_t group_id = (*rev_data)[short_code.unwrap()].group_id;
+    auto case_id = (*rev_data)[short_code.unwrap()].case_id;
 
-    return info_t {
+    return Info {
         .type_id = type_id,
         .group_id = group_id,
         .case_id = case_id,
     };
 }
+
+GroupCases::Info GroupCases::fast_obtain(codec::CommonCode common_code) {
+    return fast_obtain(common_code.to_short_code());
+}
+
+void GroupCases::build_async(klotski::Executor &&executor, klotski::Notifier &&callback) {
+
+}
+
+klotski::codec::CommonCode GroupCases::tiny_parse(klotski::cases::GroupCases::Info info) {
+    // TODO: tiny parse process
+    return CommonCode::unsafe_create(0);
+}
+
+GroupCases::Info GroupCases::tiny_obtain(codec::CommonCode common_code) {
+    // TODO: tiny obtain process
+    return Info {};
+}
diff --git a/src/core/group/internal/group_cases.inl b/src/core/group/internal/group_cases.inl
index d803a56..124ff80 100644
--- a/src/core/group/internal/group_cases.inl
+++ b/src/core/group/internal/group_cases.inl
@@ -2,28 +2,4 @@
 
 namespace klotski::cases {
 
-inline void GroupCases::build() {
-
-}
-
-inline void GroupCases::build_async(Executor &&executor, Notifier &&callback) {
-
-}
-
-inline codec::CommonCode GroupCases::parse(GroupCases::info_t info) {
-    return codec::CommonCode::unsafe_create(0);
-}
-
-inline GroupCases::info_t GroupCases::group_info(codec::RawCode raw_code) {
-    return info_t {};
-}
-
-inline GroupCases::info_t GroupCases::group_info(codec::ShortCode short_code) {
-    return info_t {};
-}
-
-inline GroupCases::info_t GroupCases::group_info(codec::CommonCode common_code) {
-    return info_t {};
-}
-
 } // namespace klotski::cases
diff --git a/src/core/main.cc b/src/core/main.cc
index 0e64083..61dea7f 100644
--- a/src/core/main.cc
+++ b/src/core/main.cc
@@ -43,11 +43,13 @@ int main() {
 //    const auto common_code = CommonCode::unsafe_create(0x1A9BF0C00);
 //    const auto group = Group::from_common_code(common_code);
 
-    std::cout << GroupCases::from_info_t({169, 1, 7472}) << std::endl;
-    std::cout << GroupCases::from_info_t({164, 0, 30833}) << std::endl;
+    GroupCases::build();
 
-    std::cout << GroupCases::to_info_t(CommonCode::unsafe_create(0x1A9BF0C00).to_short_code()) << std::endl;
-    std::cout << GroupCases::to_info_t(CommonCode::unsafe_create(0x4FEA13400).to_short_code()) << std::endl;
+    std::cout << GroupCases::fast_parse({169, 1, 7472}) << std::endl;
+    std::cout << GroupCases::fast_parse({164, 0, 30833}) << std::endl;
+
+    std::cout << GroupCases::fast_obtain(CommonCode::unsafe_create(0x1A9BF0C00)) << std::endl;
+    std::cout << GroupCases::fast_obtain(CommonCode::unsafe_create(0x4FEA13400)) << std::endl;
 
     std::cerr << std::chrono::system_clock::now() - start << std::endl;