diff --git a/src/domain/create_pokemon.rs b/src/domain/create_pokemon.rs
index 79a2406..e3466f2 100644
--- a/src/domain/create_pokemon.rs
+++ b/src/domain/create_pokemon.rs
@@ -1,3 +1,4 @@
+use std::sync::Arc;
 use crate::domain::entity::{PokemonName, PokemonNumber, PokemonTypes};
 use crate::repo::pokemon::{Insert, Repository};
 
@@ -13,7 +14,7 @@ enum Response {
     Conflict,
 }
 
-fn execute(repo: &mut dyn Repository, req: Request) -> Response {
+fn execute(repo: Arc<dyn Repository>, req: Request) -> Response {
     println!("execute");
     match (
         PokemonNumber::try_from(req.number),
@@ -23,6 +24,7 @@ fn execute(repo: &mut dyn Repository, req: Request) -> Response {
         (Ok(number), Ok(name), Ok(types)) => match repo.insert(number, name, types){
             Insert::Ok(num) => Response::Ok(u16::from(num)),
             Insert::Conflict => Response::Conflict,
+            Insert::Error => Response::BadRequest,
         },
         _ => Response::BadRequest,
     }
@@ -35,14 +37,14 @@ mod tests {
 
     #[test]
     fn it_should_return_the_pokemon_number_otherwise() {
-        let mut repo = InMemoryRepository::new();
+        let mut repo = Arc::new(InMemoryRepository::new());
         let number = 25;
         let req = Request {
             number: number,
             name: "Pikachu".to_string(),
             types: vec!["Electric".to_string(), ],
         };
-        let res = execute(&mut repo, req);
+        let res = execute(repo, req);
         match res {
             Response::Ok(num) => assert_eq!(num, number),
             _ => unreachable!(),
@@ -51,14 +53,14 @@ mod tests {
 
     #[test]
     fn it_should_return_a_bad_request_error_when_request_is_invalid() {
-        let mut repo = InMemoryRepository::new();
+        let mut repo = Arc::new(InMemoryRepository::new());
         let number = 25;
         let req = Request {
             number: number,
             name: "".to_string(),
             types: vec!["Electric".to_string(), ],
         };
-        let res = execute(&mut repo, req);
+        let res = execute(repo, req);
         match res {
             Response::Ok(num) => assert_eq!(num, number),
             Response::BadRequest => {},
@@ -71,14 +73,14 @@ mod tests {
         let number = PokemonNumber::try_from(25).unwrap();
         let name = PokemonName::try_from("Pikachu".to_string()).unwrap();
         let types = PokemonTypes::try_from(vec!["Electric".to_string(),]).unwrap();
-        let mut repo = InMemoryRepository::new();
+        let mut repo = Arc::new(InMemoryRepository::new());
         repo.insert(number, name, types);
         let req = Request {
             number: 25,
             name: "Charmander".to_string(),
             types: vec!["File".to_string()],
         };
-        let res = execute(&mut repo, req);
+        let res = execute(repo, req);
         match res {
             Response::Conflict => {},
             _ => unreachable!(),
diff --git a/src/repo/pokemon.rs b/src/repo/pokemon.rs
index c9e80ad..50b5c99 100644
--- a/src/repo/pokemon.rs
+++ b/src/repo/pokemon.rs
@@ -1,16 +1,19 @@
+use std::sync::Mutex;
 use crate::domain::entity::{Pokemon, PokemonName, PokemonNumber, PokemonTypes};
 
 pub trait Repository: Send + Sync {
-    fn insert(&mut self, number: PokemonNumber, name: PokemonName, types: PokemonTypes) -> Insert;
+    fn insert(&self, number: PokemonNumber, name: PokemonName, types: PokemonTypes) -> Insert;
 }
 #[derive(Debug)]
 pub struct InMemoryRepository {
-    pokemons: Vec<Pokemon>
+    error: bool,
+    pokemons: Mutex<Vec<Pokemon>>
 }
 impl InMemoryRepository {
     pub fn new() -> Self {
-        let pokemons: Vec<Pokemon> = vec![];
+        let pokemons: Mutex<Vec<Pokemon>> = Mutex::new(vec![]);
         Self {
+            error: false,
             pokemons
         }
     }
@@ -19,16 +22,26 @@ impl InMemoryRepository {
 pub enum Insert {
     Ok(PokemonNumber),
     Conflict,
+    Error,
 }
 
 impl Repository for InMemoryRepository {
-    fn insert(&mut self, number: PokemonNumber, name: PokemonName, types: PokemonTypes) -> Insert {
+    fn insert(&self, number: PokemonNumber, name: PokemonName, types: PokemonTypes) -> Insert {
+        if self.error {
+            return Insert::Error;
+        }
+        let mut lock = match self.pokemons.lock() {
+            Ok(lock) => lock,
+            _ => return Insert::Error,
+        };
+
+
         println!("{number:?} {:?}", self.pokemons);
-        if self.pokemons.iter().any(|pokemon| pokemon.number == number) {
+        if lock.iter().any(|pokemon| pokemon.number == number) {
             return Insert::Conflict;
         }
         let number_clone = number.clone();
-        self.pokemons.push(Pokemon::new(number_clone, name, types));
+        lock.push(Pokemon::new(number_clone, name, types));
         println!("{number:?} {:?}", self.pokemons);
         Insert::Ok(number)
     }