diff --git a/src/backend.rs b/src/backend/mod.rs
similarity index 92%
rename from src/backend.rs
rename to src/backend/mod.rs
index 85a6b32..427ca32 100644
--- a/src/backend.rs
+++ b/src/backend/mod.rs
@@ -3,6 +3,7 @@ use dashmap::DashMap;
 use std::ops::Deref;
 use std::sync::Arc;
 
+// region:    --- Enums and Structs
 #[derive(Debug, Clone)]
 pub struct Backend(Arc<BackendInner>);
 
@@ -11,7 +12,9 @@ pub struct BackendInner {
     pub(crate) map: DashMap<String, RespFrame>,
     pub(crate) hmap: DashMap<String, DashMap<String, RespFrame>>,
 }
+// endregion: --- Enums and Structs
 
+// region:    --- impls
 impl Deref for Backend {
     type Target = BackendInner;
 
@@ -63,3 +66,4 @@ impl Backend {
         self.hmap.get(key).map(|v| v.clone())
     }
 }
+// endregion: --- impls
diff --git a/src/cmd/hmap.rs b/src/cmd/hmap.rs
index 3a37f11..1642e19 100644
--- a/src/cmd/hmap.rs
+++ b/src/cmd/hmap.rs
@@ -4,6 +4,10 @@ use super::{
     extract_args, validate_command, CommandError, CommandExecutor, HGet, HGetAll, HSet, RESP_OK,
 };
 
+// region:    --- impls
+
+// endregion: --- impls
+
 impl CommandExecutor for HGet {
     fn execute(self, backend: &crate::Backend) -> RespFrame {
         match backend.hget(&self.key, &self.field) {
diff --git a/src/cmd.rs b/src/cmd/mod.rs
similarity index 97%
rename from src/cmd.rs
rename to src/cmd/mod.rs
index 5aa8988..207acb0 100644
--- a/src/cmd.rs
+++ b/src/cmd/mod.rs
@@ -8,6 +8,10 @@ mod hmap;
 mod map;
 
 // you could also use once_cell instead of lazy_static
+// lazy_static:
+// 1. init in runtime
+// 2. thread safe
+// 3. improve performance
 lazy_static! {
     static ref RESP_OK: RespFrame = SimpleString::new("OK").into();
 }
diff --git a/src/resp/decode.rs b/src/resp/decode.rs
index a511d42..4b29236 100644
--- a/src/resp/decode.rs
+++ b/src/resp/decode.rs
@@ -9,6 +9,7 @@ use super::{
     calc_total_length, extract_fixed_data, extract_simple_frame_data, parse_length, CRLF_LEN,
 };
 
+// region:    --- impls
 impl RespDecode for RespFrame {
     const PREFIX: &'static str = "";
     fn decode(buf: &mut BytesMut) -> Result<Self, RespError> {
@@ -324,6 +325,7 @@ impl RespDecode for RespSet {
         calc_total_length(buf, end, len, Self::PREFIX)
     }
 }
+// endregion: --- impls
 
 #[cfg(test)]
 mod tests {
diff --git a/src/resp/encode.rs b/src/resp/encode.rs
index cbba66c..0ab5c1d 100644
--- a/src/resp/encode.rs
+++ b/src/resp/encode.rs
@@ -10,6 +10,7 @@ use crate::{
 
 const BUF_CAP: usize = 4096;
 
+// region:    --- impls
 // - simple string: "+<string>\r\n"
 impl RespEncode for SimpleString {
     fn encode(self) -> Vec<u8> {
@@ -202,6 +203,7 @@ impl Deref for RespSet {
         &self.0
     }
 }
+// endregion: --- impls
 
 // enum_dispatch
 // 这里因为 enum_dispatch 的原因, 会自动为变体类型生成, From<xxx> for Enum_Name
diff --git a/src/resp.rs b/src/resp/mod.rs
similarity index 97%
rename from src/resp.rs
rename to src/resp/mod.rs
index 557cfc3..ba940ec 100644
--- a/src/resp.rs
+++ b/src/resp/mod.rs
@@ -9,6 +9,7 @@ mod encode;
 const CRLF: &[u8] = b"\r\n";
 const CRLF_LEN: usize = CRLF.len();
 
+// region:    --- Traits
 #[enum_dispatch]
 pub trait RespEncode {
     fn encode(self) -> Vec<u8>;
@@ -21,7 +22,9 @@ pub trait RespDecode: Sized {
     fn decode(buf: &mut BytesMut) -> Result<Self, RespError>;
     fn expect_length(buf: &[u8]) -> Result<usize, RespError>;
 }
+// endregion: --- Traits
 
+// region:    --- Enum and Structs
 #[derive(Error, Debug, PartialEq, Eq)]
 pub enum RespError {
     // region:    --- thiserror format usage
@@ -99,6 +102,9 @@ pub struct RespMap(pub(crate) BTreeMap<String, RespFrame>);
 #[derive(Debug, Clone, PartialEq)]
 pub struct RespSet(pub(crate) Vec<RespFrame>); // 改为 Vec, 用于有序的集合数据
 
+// endregion: --- Enum and Structs
+
+// region:    --- impls
 impl SimpleString {
     pub fn new(s: impl Into<String>) -> Self {
         SimpleString(s.into())
@@ -176,7 +182,9 @@ impl<const N: usize> From<&[u8; N]> for BulkString {
         BulkString(s.to_vec())
     }
 }
+// endregion: --- impls
 
+// region:    --- Functions
 // utility functions
 fn extract_fixed_data(
     buf: &mut BytesMut,
@@ -265,3 +273,5 @@ fn calc_total_length(buf: &[u8], end: usize, len: usize, prefix: &str) -> Result
         _ => Ok(len + CRLF_LEN),
     }
 }
+
+// endregion: --- Functions