diff --git a/backend/Cargo.toml b/backend/Cargo.toml
index e9b5c95..b294c0c 100644
--- a/backend/Cargo.toml
+++ b/backend/Cargo.toml
@@ -15,7 +15,7 @@ lazy_static = "1.3.0"
 mime_guess = "1.8.7"
 openssl-probe = "0.1.2"
 pretty_env_logger = "0.3.0"
-serde = "1.0.97"
+serde = { version = "1.0.97", features = ["rc"] }
 serde_derive = "1.0.97"
 serde_json = "1.0.40"
 structopt = "0.2.18"
diff --git a/backend/src/cache.rs b/backend/src/cache.rs
index 9ca559d..dd0a36c 100644
--- a/backend/src/cache.rs
+++ b/backend/src/cache.rs
@@ -1,6 +1,7 @@
 use std::{
     collections::HashMap,
     hash::Hash,
+    sync::Arc,
     time::{Duration, Instant},
 };
 
@@ -67,7 +68,7 @@ impl<T> CacheEntry<T> {
 }
 
 #[derive(Eq, PartialEq, Hash, Debug)]
-pub(crate) struct Key(Service, String, String, String);
+pub(crate) struct Key(Service, Arc<String>, Arc<String>, Arc<String>);
 
 #[derive(Eq, PartialEq, Hash, Debug)]
 pub(crate) enum Service {
@@ -77,7 +78,12 @@ pub(crate) enum Service {
 }
 
 impl Key {
-    pub(crate) fn new(service: Service, user: String, repo: String, branch: String) -> Self {
+    pub(crate) fn new(
+        service: Service,
+        user: Arc<String>,
+        repo: Arc<String>,
+        branch: Arc<String>,
+    ) -> Self {
         Key(service, user, repo, branch)
     }
 }
diff --git a/backend/src/data.rs b/backend/src/data.rs
index 5439e68..7f36ab0 100644
--- a/backend/src/data.rs
+++ b/backend/src/data.rs
@@ -8,10 +8,10 @@ pub(crate) type State = Arc<RwLock<Cache<Key, String>>>;
 
 #[derive(Deserialize, Debug)]
 pub(crate) struct FilePath {
-    pub(crate) user: String,
-    pub(crate) repo: String,
-    pub(crate) commit: String,
-    pub(crate) file: String,
+    pub(crate) user: Arc<String>,
+    pub(crate) repo: Arc<String>,
+    pub(crate) commit: Arc<String>,
+    pub(crate) file: Arc<String>,
 }
 
 impl FilePath {
diff --git a/backend/src/main.rs b/backend/src/main.rs
index 36a7177..20bd518 100644
--- a/backend/src/main.rs
+++ b/backend/src/main.rs
@@ -7,8 +7,6 @@ extern crate serde_derive;
 #[macro_use]
 extern crate structopt;
 
-// TODO: cow instead of string
-
 mod cache;
 mod cdn;
 mod config;
@@ -51,7 +49,7 @@ fn proxy_file<T: Service>(
             .from_err()
             .and_then(move |response| match response.status() {
                 StatusCode::OK => {
-                    let mime = mime_guess::guess_mime_type(&data.file);
+                    let mime = mime_guess::guess_mime_type(&*data.file);
                     Ok(HttpResponse::Ok()
                         .content_type(mime.to_string().as_str())
                         .set(CacheControl(vec![
@@ -134,7 +132,7 @@ fn serve_gist(
         .from_err()
         .and_then(move |response| match response.status() {
             StatusCode::OK => {
-                let mime = mime_guess::guess_mime_type(&data.file);
+                let mime = mime_guess::guess_mime_type(&*data.file);
                 Ok(HttpResponse::Ok()
                     .content_type(mime.to_string().as_str())
                     .set(CacheControl(vec![