diff --git a/README.md b/README.md
index a60b4b4..dbc9619 100644
--- a/README.md
+++ b/README.md
@@ -5,26 +5,33 @@
 
 ## Introduction
 
-Galois is an extremely high performance matching engine written in Rust which uses event-sourcing pattern to handle tens of thousands of orders per second or even better, depending on the performance of persistence. 
+Galois is an extremely high-performance matching engine written in Rust which uses event-sourcing pattern to handle tens of thousands of orders per second or even better.
+
+The internal structure of Galois looks like below:
 
 ```
+
            sidecar   chain <-+
-             |         |      \
+             ^         |      \
              |         |       \
              v         v        \
-   +-----> server   scanner      +
+   +---->  server   scanner      +
    |          \       /          |
    |\          \     /           |
    | \          \   /            |
-   |  +-<-    sequencer          |
+   |  +--     sequencer          |
    +              |              |
    |\             |              |
    | \            v              |
-   |  +-<-    executor           |
-   +            /   \            +
-    \          /     \          /
-     \        /       \        /
-      +-<- output  committer -+
+   |  +--      executor          |
+   |              |              |
+   |              |              |
+   |              v              |
+   +           rocksdb           +
+    \           /   \           /
+     \         /     \         /
+      \       /       \       /
+       +-- market committer -+
 
 ```
 
diff --git a/engine/src/executor/orderbook.rs b/engine/src/executor/orderbook.rs
index 15d8573..7e7e4bb 100644
--- a/engine/src/executor/orderbook.rs
+++ b/engine/src/executor/orderbook.rs
@@ -164,7 +164,7 @@ pub struct OrderBook {
     pub min_vol: Amount,
     pub enable_market_order: bool,
     pub open: bool,
-    max_id: OrderId,
+    pub max_id: OrderId,
 }
 
 #[derive(Serialize, Deserialize, Debug, Clone, Eq, PartialEq)]
diff --git a/engine/src/migration.rs b/engine/src/migration.rs
index 3e4f14d..b56e955 100644
--- a/engine/src/migration.rs
+++ b/engine/src/migration.rs
@@ -43,10 +43,10 @@ mod v1_to_v2 {
             futures::executor::block_on(async move { Pool::connect_with(option).await.unwrap() });
         let mut pendings = vec![];
         let pool = std::sync::Arc::new(pool);
-        for (symbol, _) in data.orderbooks.iter() {
+        for (symbol, orderbook) in data.orderbooks.iter() {
             let sql = format!(
-                "select * from t_order_{}_{} where f_status in (0, 3)",
-                symbol.0, symbol.1
+                "select * from t_order_{}_{} where f_status in (0, 3) and f_id <= {}",
+                symbol.0, symbol.1, orderbook.max_id,
             );
             let s = *symbol;
             let p = pool.clone();