diff --git a/src/main.rs b/src/main.rs
index a7eb618..add8884 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,3 +1,5 @@
+#![feature(let_chains)]
+
 use std::process::{Command, Stdio};
 use std::sync::mpsc;
 use std::{env, path::Path};
@@ -5,7 +7,7 @@ use std::{env, path::Path};
 use log::{debug, trace};
 use serde::{Deserialize, Serialize};
 use serde_json;
-use tokio;
+use tokio::sync::Semaphore;
 
 const UPSTREAM_CACHES: &'static [&'static str] = &[
     "https://cache.nixos.org",
@@ -75,71 +77,91 @@ async fn main() {
     let store_paths = path_infos[0].get_store_paths();
     let (cacheable_tx, cacheable_rx) = mpsc::channel();
 
+    let mut handles = Vec::new();
+    
     println!("spawning check_upstream");
-    tokio::spawn(async move {
+    handles.push(tokio::spawn(async move {
         check_upstream(store_paths, cacheable_tx).await;
-    });
+    }));
 
     println!("spawning uploader");
-    tokio::spawn(async move {
+    handles.push(tokio::spawn(async move {
         uploader(cacheable_rx).await;
-    }).await.unwrap();
+    }));
+
+    // make sure all threads are done
+    for handle in handles {
+        handle.await.unwrap();
+    }
 }
 
 // filter out store paths that exist in upstream caches
 async fn check_upstream(store_paths: Vec<String>, cacheable_tx: mpsc::Sender<String>) {
+    let concurrent = Semaphore::new(50);
     for store_path in store_paths {
-        let basename = Path::new(&store_path)
-            .file_name()
-            .unwrap()
-            .to_str()
-            .unwrap()
-            .to_string();
-        let hash = basename.split("-").nth(0).unwrap();
-
-        let mut hit = false;
-        for upstream in UPSTREAM_CACHES {
-            let mut uri = String::from(*upstream);
-            uri.push_str(format!("/{}.narinfo", hash).as_str());
-
-            let res_status = reqwest::Client::new()
-                .head(uri)
-                .send()
-                .await
+        let _ = concurrent.acquire().await.unwrap();
+        let tx = cacheable_tx.clone();
+        tokio::spawn(async move {
+            let basename = Path::new(&store_path)
+                .file_name()
                 .unwrap()
-                .status();
+                .to_str()
+                .unwrap()
+                .to_string();
+            let hash = basename.split("-").nth(0).unwrap();
 
-            if res_status.is_success() {
-                debug!("{} was a hit upstream: {}", store_path, upstream);
-                hit = true;
-                break;
+            let mut hit = false;
+            for upstream in UPSTREAM_CACHES {
+                let mut uri = String::from(*upstream);
+                uri.push_str(format!("/{}.narinfo", hash).as_str());
+
+                let res_status = reqwest::Client::new()
+                    .head(uri)
+                    .send()
+                    .await
+                    .map(|x| x.status());
+
+                if let Ok(res_status) = res_status && res_status.is_success() {
+                    println!("{} was a hit upstream: {}", store_path, upstream);
+                    hit = true;
+                    break;
+                }
             }
-        }
-        if !hit {
-            trace!("sending {}", store_path);
-            cacheable_tx.send(store_path).unwrap();
-        }
+            if !hit {
+                trace!("sending {}", store_path);
+                tx.send(store_path).unwrap();
+            }
+        });
     }
 }
 
 async fn uploader(cacheable_rx: mpsc::Receiver<String>) {
     let mut count = 0;
+    let concurrent = Semaphore::new(10);
+    let mut handles = Vec::new();
     loop {
         if let Ok(path_to_upload) = cacheable_rx.recv() {
-            trace!("to upload: {}", path_to_upload);
-            if Command::new("nix")
-                .arg("copy")
-                .arg("--to")
-                .arg("s3://nixcache?endpoint=s3.cy7.sh&secret-key=/home/yt/cache-priv-key.pem")
-                .arg(&path_to_upload)
-                .output()
-                .is_err()
-            {
-                println!("WARN: upload failed: {}", path_to_upload);
-            } else {
-                count += 1;
-            }
+            let _ = concurrent.acquire().await.unwrap();
+            handles.push(tokio::spawn(async move {
+                println!("uploading: {}", path_to_upload);
+                if Command::new("nix")
+                    .arg("copy")
+                    .arg("--to")
+                    .arg("s3://nixcache?endpoint=s3.cy7.sh&secret-key=/home/yt/cache-priv-key.pem")
+                    .arg(&path_to_upload)
+                    .output()
+                    .is_err()
+                {
+                    println!("WARN: upload failed: {}", path_to_upload);
+                } else {
+                    count += 1;
+                }
+            }));
         } else {
+            // make sure all threads are done
+            for handle in handles {
+                handle.await.unwrap();
+            }
             println!("uploaded {} paths", count);
             break;
         }