diff --git a/src/config.rs b/src/config.rs
index 14d6d74..4999fc2 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -5,8 +5,9 @@ use serde::{Deserialize, Serialize};
 pub struct HostConfig {
     pub brain_url: String,
     pub host_ip_address: String,
-    pub operator_pubkey: String,
+    pub operator_wallet: String,
     pub max_cores_per_app: u32,
+    pub max_memory_mb_per_app: u32,
     pub max_vcpu_reservation: u32,
     pub max_mem_reservation_mb: u32,
     pub max_disk_reservation_mb: u32,
@@ -24,37 +25,6 @@ fn default_reserved_no_of_port() -> u32 {
     16
 }
 
-/*
-impl Default for HostConfig {
-    fn default() -> Self {
-        // TODO: load from config file
-        let brain_url =
-            std::env::var("BRAIN_URL").unwrap_or_else(|_| "http://127.0.0.1:31337".to_string());
-        let owner_wallet = "0x".to_string();
-        let host_ip_address = "127.0.0.1".to_string();
-
-        let max_cores_per_app = 4;
-        let max_vcpu_reservation = 8;
-        let max_mem_reservation_mb = 8192;
-        let max_ports_per_app = 9;
-        let price = 0;
-
-        Self {
-            brain_url,
-            host_ip_address,
-            owner_wallet,
-            max_cores_per_app,
-            max_ports_per_app,
-            max_vcpu_reservation,
-            max_mem_reservation_mb,
-            price,
-
-            delete_archive: true,
-        }
-    }
-}
-*/
-
 impl HostConfig {
     pub fn load_from_disk(path: &str) -> Result<Self> {
         let content = std::fs::read_to_string(path)?;
diff --git a/src/data.rs b/src/data.rs
index 4d6a68a..51d9863 100644
--- a/src/data.rs
+++ b/src/data.rs
@@ -92,11 +92,28 @@ impl App {
         host_config: &HostConfig,
         host_resource: &mut HostResources,
     ) -> Result<Self> {
+        if new_app_req.price_per_unit < host_config.price {
+            return Err(anyhow!("price is too low"));
+        }
+
+        if host_resource.existing_apps.contains(&new_app_req.uuid) {
+            let content =
+                std::fs::read_to_string(format!("{}{}.yaml", *APP_CONFIG_DIR, &new_app_req.uuid))?;
+            let app: App = serde_yml::from_str(&content)?;
+            return Err(anyhow!("app already exists\n{:?}", app));
+        }
+
         let app_uuid = new_app_req.uuid.clone();
 
         if host_config.max_cores_per_app < new_app_req.resource.vcpu {
             return Err(anyhow!("too many vcpus for app"));
         }
+
+        if host_config.max_memory_mb_per_app < new_app_req.resource.memory_mb {
+            return Err(anyhow!("too much memory for app"));
+        }
+
+        // TODO: revert state if any error
         if host_config.max_vcpu_reservation
             < host_resource
                 .reserved_vcpus
diff --git a/src/grpc.rs b/src/grpc.rs
index 8740be0..49a60bf 100644
--- a/src/grpc.rs
+++ b/src/grpc.rs
@@ -30,11 +30,12 @@ pub async fn register_node(config: &crate::HostConfig) -> Result<Vec<AppContract
 
     let req = RegisterAppNodeReq {
         node_pubkey: PUBLIC_KEY.to_string(),
-        operator_pubkey: config.operator_pubkey.clone(),
+        operator_wallet: config.operator_wallet.clone(),
         main_ip: IP_INFO.ip.clone(),
         city: IP_INFO.city.clone(),
         region: IP_INFO.region.clone(),
         country: IP_INFO.country.clone(),
+        price: config.price,
     };
 
     let pubkey = PUBLIC_KEY.clone();