diff --git a/README.md b/README.md
index c304781..d68902e 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,7 @@
 # zino
 
-`zino` is a full featured web application framework which focuses on productivity and performance.
+`zino` is a full featured web application framework for Rust which focuses on
+productivity and performance.
 
 [![Crates.io](https://img.shields.io/crates/v/zino)][zino]
 [![Documentation](https://shields.io/docsrs/zino)][zino-docs]
diff --git a/examples/axum-app/app/src/controller/user.rs b/examples/axum-app/app/src/controller/user.rs
index 1513079..4ab7420 100644
--- a/examples/axum-app/app/src/controller/user.rs
+++ b/examples/axum-app/app/src/controller/user.rs
@@ -1,6 +1,6 @@
 use serde_json::json;
-use zino::Request;
-use zino_core::{Model, Query, Rejection, RequestContext, Response, Schema, Uuid};
+use zino::{AxumCluster, Request};
+use zino_core::{Application, Model, Query, Rejection, RequestContext, Response, Schema, Uuid};
 use zino_model::User;
 
 pub(crate) async fn new(mut req: Request) -> zino::Result {
@@ -63,7 +63,8 @@ pub(crate) async fn view(mut req: Request) -> zino::Result {
 
     let data = json!({
         "user": user,
-        "state": state_data,
+        "app_state_data": AxumCluster::state_data(),
+        "state_data": state_data,
         "config": req.config(),
     });
     res.set_data(data);
diff --git a/examples/axum-app/config/config.dev.toml b/examples/axum-app/config/config.dev.toml
index bfc4496..7abe01a 100644
--- a/examples/axum-app/config/config.dev.toml
+++ b/examples/axum-app/config/config.dev.toml
@@ -1,6 +1,6 @@
 
 name = "data-cube"
-version = "0.2.2"
+version = "0.3.0"
 
 [main]
 host = "127.0.0.1"
diff --git a/examples/axum-app/config/config.prod.toml b/examples/axum-app/config/config.prod.toml
index 50c9f14..1b551ca 100644
--- a/examples/axum-app/config/config.prod.toml
+++ b/examples/axum-app/config/config.prod.toml
@@ -1,6 +1,6 @@
 
 name = "data-cube"
-version = "0.2.2"
+version = "0.3.0"
 
 [main]
 host = "127.0.0.1"
diff --git a/zino-core/src/application.rs b/zino-core/src/application.rs
index ec15e90..1a65bda 100644
--- a/zino-core/src/application.rs
+++ b/zino-core/src/application.rs
@@ -1,5 +1,5 @@
-use crate::{AsyncCronJob, CronJob, Job, JobScheduler, State};
-use std::{collections::HashMap, sync::LazyLock, thread, time::Instant};
+use crate::{AsyncCronJob, CronJob, Job, JobScheduler, Map, State};
+use std::{collections::HashMap, thread};
 use toml::value::Table;
 
 /// Application.
@@ -10,8 +10,8 @@ pub trait Application {
     /// Creates a new application.
     fn new() -> Self;
 
-    /// Returns the start time.
-    fn start_time(&self) -> Instant;
+    /// Returns a reference to the shared application state.
+    fn shared() -> &'static State;
 
     /// Registers routes.
     fn register(self, routes: HashMap<&'static str, Self::Router>) -> Self;
@@ -22,13 +22,19 @@ pub trait Application {
     /// Returns the application env.
     #[inline]
     fn env() -> &'static str {
-        SHARED_STATE.env()
+        Self::shared().env()
     }
 
-    /// Returns a reference to the application scoped config.
+    /// Returns a reference to the shared application config.
     #[inline]
     fn config() -> &'static Table {
-        SHARED_STATE.config()
+        Self::shared().config()
+    }
+
+    /// Returns a reference to the shared application state data.
+    #[inline]
+    fn state_data() -> &'static Map {
+        Self::shared().data()
     }
 
     /// Spawns a new thread to run cron jobs.
@@ -47,6 +53,3 @@ pub trait Application {
         self
     }
 }
-
-/// Shared application state.
-static SHARED_STATE: LazyLock<State> = LazyLock::new(State::default);
diff --git a/zino-core/src/database/column.rs b/zino-core/src/database/column.rs
index c08d5f2..fe8988b 100644
--- a/zino-core/src/database/column.rs
+++ b/zino-core/src/database/column.rs
@@ -4,7 +4,7 @@ use serde::Serialize;
 use serde_json::Value;
 use sqlx::{postgres::PgRow, Column as _, Error, Row, TypeInfo};
 
-/// A column is a model field with associated metadata.
+/// A model field with associated metadata.
 #[derive(Debug, Clone, Serialize)]
 pub struct Column<'a> {
     /// Column name.
diff --git a/zino-core/src/database/mod.rs b/zino-core/src/database/mod.rs
index 331eb64..b1f625b 100644
--- a/zino-core/src/database/mod.rs
+++ b/zino-core/src/database/mod.rs
@@ -1,4 +1,4 @@
-use crate::{crypto, State};
+use crate::{crypto, state::SHARED_STATE};
 use sqlx::{
     postgres::{PgConnectOptions, PgPoolOptions},
     PgPool,
@@ -167,21 +167,31 @@ impl ConnectionPool {
     }
 }
 
-/// Shared state.
-pub(super) static SHARED_STATE: LazyLock<State> = LazyLock::new(|| {
-    let mut state = State::default();
+/// A list of database connection pools.
+#[derive(Debug, Clone)]
+pub(crate) struct ConnectionPools(Vec<ConnectionPool>);
+
+impl ConnectionPools {
+    /// Returns a connection pool with the specific name.
+    #[inline]
+    pub(crate) fn get_pool(&self, name: &str) -> Option<&ConnectionPool> {
+        self.0.iter().find(|c| c.name() == name)
+    }
+}
+
+/// Shared connection pools.
+pub(super) static SHARED_CONNECTION_POOLS: LazyLock<ConnectionPools> = LazyLock::new(|| {
+    let config = SHARED_STATE.config();
 
     // Application name.
-    let application_name = state
-        .config()
+    let application_name = config
         .get("name")
         .and_then(|t| t.as_str())
         .expect("the `name` field should be specified");
 
     // Database connection pools.
     let mut pools = Vec::new();
-    let databases = state
-        .config()
+    let databases = config
         .get("postgres")
         .expect("the `postgres` field should be specified")
         .as_array()
@@ -195,10 +205,7 @@ pub(super) static SHARED_STATE: LazyLock<State> = LazyLock::new(|| {
             pools.push(pool);
         }
     }
-    if !pools.is_empty() {
-        state.set_pools(pools);
-    }
-    state
+    ConnectionPools(pools)
 });
 
 /// Database namespace prefix.
diff --git a/zino-core/src/database/schema.rs b/zino-core/src/database/schema.rs
index aeb5075..06711ba 100644
--- a/zino-core/src/database/schema.rs
+++ b/zino-core/src/database/schema.rs
@@ -57,7 +57,7 @@ pub trait Schema: 'static + Send + Sync + Model {
     /// Initializes the model reader.
     #[inline]
     fn init_reader() -> Result<&'static ConnectionPool, Error> {
-        super::SHARED_STATE
+        super::SHARED_CONNECTION_POOLS
             .get_pool(Self::READER_NAME)
             .ok_or(Error::PoolClosed)
     }
@@ -65,7 +65,7 @@ pub trait Schema: 'static + Send + Sync + Model {
     /// Initializes the model writer.
     #[inline]
     fn init_writer() -> Result<&'static ConnectionPool, Error> {
-        super::SHARED_STATE
+        super::SHARED_CONNECTION_POOLS
             .get_pool(Self::WRITER_NAME)
             .ok_or(Error::PoolClosed)
     }
diff --git a/zino-core/src/datetime.rs b/zino-core/src/datetime.rs
index 943db0b..2b6c781 100644
--- a/zino-core/src/datetime.rs
+++ b/zino-core/src/datetime.rs
@@ -3,6 +3,7 @@ use chrono::{
     Local, SecondsFormat, TimeZone, Utc,
 };
 use serde::{Deserialize, Serialize};
+use serde_json::Value;
 use std::{
     fmt,
     ops::{Add, AddAssign, Sub, SubAssign},
@@ -64,15 +65,16 @@ impl DateTime {
     /// Returns an RFC 2822 date and time string.
     #[inline]
     pub fn to_utc_string(&self) -> String {
-        let datetime = self.0.with_timezone(&Utc).to_rfc2822();
-        format!("{} GMT", datetime.trim_end_matches(" +0000"))
+        let datetime = self.0.with_timezone(&Utc);
+        format!("{} GMT", datetime.to_rfc2822().trim_end_matches(" +0000"))
     }
 
     /// Return an RFC 3339 and ISO 8601 date and time string with subseconds
     /// formatted as [`SecondsFormat::Millis`](chrono::SecondsFormat::Millis).
     #[inline]
     pub fn to_iso_string(&self) -> String {
-        self.0.to_rfc3339_opts(SecondsFormat::Millis, true)
+        let datetime = self.0.with_timezone(&Utc);
+        datetime.to_rfc3339_opts(SecondsFormat::Millis, true)
     }
 }
 
@@ -83,15 +85,21 @@ impl Default for DateTime {
     }
 }
 
+impl From<chrono::DateTime<Local>> for DateTime {
+    fn from(dt: chrono::DateTime<Local>) -> Self {
+        Self(dt)
+    }
+}
+
 impl From<DateTime> for chrono::DateTime<Local> {
     fn from(dt: DateTime) -> Self {
         dt.0
     }
 }
 
-impl From<chrono::DateTime<Local>> for DateTime {
-    fn from(dt: chrono::DateTime<Local>) -> Self {
-        Self(dt)
+impl From<DateTime> for Value {
+    fn from(dt: DateTime) -> Self {
+        Value::String(dt.to_string())
     }
 }
 
diff --git a/zino-core/src/request/mod.rs b/zino-core/src/request/mod.rs
index f2ee746..02c0f13 100644
--- a/zino-core/src/request/mod.rs
+++ b/zino-core/src/request/mod.rs
@@ -16,7 +16,7 @@ pub use validation::Validation;
 
 /// Request context.
 pub trait RequestContext {
-    /// Returns a reference to the application scoped config.
+    /// Returns a reference to the application config.
     fn config(&self) -> &Table;
 
     /// Returns a reference to the request scoped state data.
diff --git a/zino-core/src/state.rs b/zino-core/src/state.rs
index 3c1a4c5..7ff1d04 100644
--- a/zino-core/src/state.rs
+++ b/zino-core/src/state.rs
@@ -1,5 +1,5 @@
-use crate::{ConnectionPool, Map};
-use std::{env, fs, path::Path};
+use crate::Map;
+use std::{env, fs, path::Path, sync::LazyLock};
 use toml::value::{Table, Value};
 
 /// Application state.
@@ -9,8 +9,6 @@ pub struct State {
     env: String,
     /// Configuration.
     config: Table,
-    /// Connection pools.
-    pools: Vec<ConnectionPool>,
     /// Associated data.
     data: Map,
 }
@@ -22,7 +20,6 @@ impl State {
         Self {
             env,
             config: Table::new(),
-            pools: Vec::new(),
             data: Map::new(),
         }
     }
@@ -46,6 +43,12 @@ impl State {
         }
     }
 
+    /// Set the state data.
+    #[inline]
+    pub fn set_data(&mut self, data: Map) {
+        self.data = data;
+    }
+
     /// Returns the env as `&str`.
     #[inline]
     pub fn env(&self) -> &str {
@@ -73,7 +76,7 @@ impl State {
     /// Returns a list of listeners as `Vec<String>`.
     pub fn listeners(&self) -> Vec<String> {
         let config = self.config();
-        let mut listeners = vec![];
+        let mut listeners = Vec::new();
 
         // Main server.
         let main = config
@@ -122,32 +125,24 @@ impl State {
 
         listeners
     }
-
-    /// Returns a connection pool with the specific name.
-    #[inline]
-    pub(crate) fn get_pool(&self, name: &str) -> Option<&ConnectionPool> {
-        self.pools.iter().find(|c| c.name() == name)
-    }
-
-    /// Sets the connection pools.
-    #[inline]
-    pub(crate) fn set_pools(&mut self, pools: Vec<ConnectionPool>) {
-        self.pools = pools;
-    }
 }
 
 impl Default for State {
-    #[inline]
     fn default() -> Self {
-        let mut app_env = "dev".to_string();
-        for arg in env::args() {
-            if arg.starts_with("--env=") {
-                app_env = arg.strip_prefix("--env=").unwrap().to_string();
-            }
-        }
-
-        let mut state = State::new(app_env);
-        state.load_config();
-        state
+        SHARED_STATE.clone()
     }
 }
+
+/// Shared application state.
+pub(crate) static SHARED_STATE: LazyLock<State> = LazyLock::new(|| {
+    let mut app_env = "dev".to_string();
+    for arg in env::args() {
+        if arg.starts_with("--env=") {
+            app_env = arg.strip_prefix("--env=").unwrap().to_string();
+        }
+    }
+
+    let mut state = State::new(app_env);
+    state.load_config();
+    state
+});
diff --git a/zino/Cargo.toml b/zino/Cargo.toml
index 1b4d0c2..20f3681 100644
--- a/zino/Cargo.toml
+++ b/zino/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "zino"
-description = "A full featured web application framework."
+description = "Full featured web application framework for Rust."
 version = "0.3.0"
 rust-version = "1.68"
 edition = "2021"
diff --git a/zino/README.md b/zino/README.md
index b5a6201..586cbc4 100644
--- a/zino/README.md
+++ b/zino/README.md
@@ -1,6 +1,7 @@
 # zino
 
-`zino` is a full featured web application framework which focuses on productivity and performance.
+`zino` is a full featured web application framework for Rust which focuses on
+productivity and performance.
 
 ## Highlights
 
diff --git a/zino/src/channel/axum_channel.rs b/zino/src/channel/axum_channel.rs
index 2187fa5..8141e6f 100644
--- a/zino/src/channel/axum_channel.rs
+++ b/zino/src/channel/axum_channel.rs
@@ -117,8 +117,9 @@ impl Default for MessageChannel {
 }
 
 /// Channel capacity.
-static CHANNEL_CAPACITY: LazyLock<usize> =
-    LazyLock::new(|| match crate::AxumCluster::config().get("channel") {
+static CHANNEL_CAPACITY: LazyLock<usize> = LazyLock::new(|| {
+    let config = crate::AxumCluster::config();
+    match config.get("channel") {
         Some(config) => config
             .as_table()
             .expect("the `channel` field should be a table")
@@ -129,7 +130,8 @@ static CHANNEL_CAPACITY: LazyLock<usize> =
             .try_into()
             .expect("the `channel.capacity` field should be a positive integer"),
         None => 10000,
-    });
+    }
+});
 
 /// Channel subscribers.
 static CHANNEL_SUBSCRIBERS: LazyLock<RwLock<HashMap<Uuid, Subscriber>>> =
diff --git a/zino/src/cluster/axum_cluster.rs b/zino/src/cluster/axum_cluster.rs
index 5597fd7..6801643 100644
--- a/zino/src/cluster/axum_cluster.rs
+++ b/zino/src/cluster/axum_cluster.rs
@@ -12,8 +12,8 @@ use std::{
     env, io,
     net::SocketAddr,
     path::Path,
-    sync::{Arc, LazyLock},
-    time::{Duration, Instant},
+    sync::LazyLock,
+    time::Duration,
 };
 use tokio::runtime::Builder;
 use tower::{
@@ -27,12 +27,10 @@ use tower_http::{
 };
 use tracing::Level;
 use tracing_subscriber::fmt::{time, writer::MakeWriterExt};
-use zino_core::{Application, AsyncCronJob, Job, JobScheduler, Response, State};
+use zino_core::{Application, AsyncCronJob, DateTime, Job, JobScheduler, Map, Response, State};
 
 /// An HTTP server cluster for `axum`.
 pub struct AxumCluster {
-    /// Start time.
-    start_time: Instant,
     /// Routes.
     routes: HashMap<&'static str, Router>,
 }
@@ -98,15 +96,14 @@ impl Application for AxumCluster {
             .init();
 
         Self {
-            start_time: Instant::now(),
             routes: HashMap::new(),
         }
     }
 
-    /// Returns the start time.
+    /// Returns a reference to the shared application state.
     #[inline]
-    fn start_time(&self) -> Instant {
-        self.start_time
+    fn shared() -> &'static State {
+        LazyLock::force(&SHARED_CLUSTER_STATE)
     }
 
     /// Registers routes.
@@ -171,7 +168,7 @@ impl Application for AxumCluster {
                     app = app.nest(path, route.clone());
                 }
 
-                let state = Arc::new(app_state.clone());
+                let state = app_state.clone();
                 app = app
                     .fallback_service(tower::service_fn(|_| async {
                         let res = Response::new(StatusCode::NOT_FOUND);
@@ -220,3 +217,24 @@ impl Application for AxumCluster {
         });
     }
 }
+
+/// Shared cluster state.
+static SHARED_CLUSTER_STATE: LazyLock<State> = LazyLock::new(|| {
+    let mut state = State::default();
+    let config = state.config();
+    let app_name = config
+        .get("name")
+        .and_then(|t| t.as_str())
+        .expect("the `name` field should be specified");
+    let app_version = config
+        .get("version")
+        .and_then(|t| t.as_str())
+        .expect("the `version` field should be specified");
+
+    let mut data = Map::new();
+    data.insert("app_name".to_string(), app_name.into());
+    data.insert("app_version".to_string(), app_version.into());
+    data.insert("cluster_start_at".to_string(), DateTime::now().into());
+    state.set_data(data);
+    state
+});
diff --git a/zino/src/lib.rs b/zino/src/lib.rs
index db8e4f9..b37d019 100644
--- a/zino/src/lib.rs
+++ b/zino/src/lib.rs
@@ -1,4 +1,5 @@
-//! [`zino`] is a full featured web application framework which focuses on productivity and performance.
+//! [`zino`] is a full featured web application framework for Rust
+//! which focuses on productivity and performance.
 //!
 //! ## Highlights
 //!
diff --git a/zino/src/middleware/tower_cors.rs b/zino/src/middleware/tower_cors.rs
index 13b485b..0b6a390 100644
--- a/zino/src/middleware/tower_cors.rs
+++ b/zino/src/middleware/tower_cors.rs
@@ -4,10 +4,8 @@ use zino_core::Application;
 
 // CORS middleware.
 pub(crate) static CORS_MIDDLEWARE: LazyLock<CorsLayer> = LazyLock::new(|| {
-    match crate::AxumCluster::config()
-        .get("cors")
-        .and_then(|t| t.as_table())
-    {
+    let config = crate::AxumCluster::config();
+    match config.get("cors").and_then(|t| t.as_table()) {
         Some(cors) => {
             let allow_credentials = cors
                 .get("allow-credentials")
diff --git a/zino/src/request/axum_request.rs b/zino/src/request/axum_request.rs
index 06e06cb..e9fd8a8 100644
--- a/zino/src/request/axum_request.rs
+++ b/zino/src/request/axum_request.rs
@@ -10,7 +10,6 @@ use serde::de::DeserializeOwned;
 use std::{
     convert::Infallible,
     ops::{Deref, DerefMut},
-    sync::Arc,
 };
 use toml::value::Table;
 use zino_core::{CloudEvent, Context, Map, Rejection, RequestContext, State, Validation};
@@ -37,18 +36,18 @@ impl<T> DerefMut for AxumExtractor<T> {
 impl RequestContext for AxumExtractor<Request<Body>> {
     #[inline]
     fn config(&self) -> &Table {
-        let state = self.extensions().get::<Arc<State>>().unwrap();
+        let state = self.extensions().get::<State>().unwrap();
         state.config()
     }
 
     fn state_data(&self) -> &Map {
-        let state = self.extensions().get::<Arc<State>>().unwrap();
+        let state = self.extensions().get::<State>().unwrap();
         state.data()
     }
 
     fn state_data_mut(&mut self) -> &mut Map {
-        let state = self.extensions_mut().get_mut::<Arc<State>>().unwrap();
-        Arc::make_mut(state).data_mut()
+        let state = self.extensions_mut().get_mut::<State>().unwrap();
+        state.data_mut()
     }
 
     #[inline]