diff --git a/Cargo.lock b/Cargo.lock
index 89dbb35..982b17f 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -104,7 +104,6 @@ dependencies = [
  "anyhow",
  "aquatic_cli_helpers",
  "aquatic_http_protocol",
- "hashbrown",
  "mimalloc",
  "mio",
  "quickcheck",
@@ -112,6 +111,7 @@ dependencies = [
  "rand",
  "rand_distr",
  "serde",
+ "slab",
 ]
 
 [[package]]
@@ -1680,6 +1680,12 @@ dependencies = [
  "termcolor",
 ]
 
+[[package]]
+name = "slab"
+version = "0.4.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c111b5bd5695e56cffe5129854aa230b39c93a305372fdbb2668ca2394eea9f8"
+
 [[package]]
 name = "smallvec"
 version = "1.4.0"
diff --git a/TODO.md b/TODO.md
index 55b3e5b..f7c5d39 100644
--- a/TODO.md
+++ b/TODO.md
@@ -10,7 +10,6 @@
 
 ## aquatic_http_load_test
 
-* use slab for connections? HashMap not necessary
 * request sending: too many allocations, likely due to request to byte
   conversion. optimize!
 * think about when to open new connections
diff --git a/aquatic_http_load_test/Cargo.toml b/aquatic_http_load_test/Cargo.toml
index 9fde658..0314652 100644
--- a/aquatic_http_load_test/Cargo.toml
+++ b/aquatic_http_load_test/Cargo.toml
@@ -12,12 +12,12 @@ name = "aquatic_http_load_test"
 anyhow = "1"
 aquatic_cli_helpers = { path = "../aquatic_cli_helpers" }
 aquatic_http_protocol = { path = "../aquatic_http_protocol" }
-hashbrown = { version = "0.7", features = ["serde"] }
 mimalloc = { version = "0.1", default-features = false }
 mio = { version = "0.7", features = ["udp", "os-poll", "os-util"] }
 rand = { version = "0.7", features = ["small_rng"] }
 rand_distr = "0.2"
 serde = { version = "1", features = ["derive"] }
+slab = "0.4"
 
 [dev-dependencies]
 quickcheck = "0.9"
diff --git a/aquatic_http_load_test/src/network.rs b/aquatic_http_load_test/src/network.rs
index 1fd1c96..fa918f5 100644
--- a/aquatic_http_load_test/src/network.rs
+++ b/aquatic_http_load_test/src/network.rs
@@ -2,9 +2,9 @@ use std::sync::atomic::Ordering;
 use std::time::Duration;
 use std::io::{Read, Write, ErrorKind};
 
-use hashbrown::HashMap;
 use mio::{net::TcpStream, Events, Poll, Interest, Token};
 use rand::{rngs::SmallRng, prelude::*};
+use slab::Slab;
 
 use crate::common::*;
 use crate::config::*;
@@ -27,6 +27,10 @@ impl Connection {
         token_counter: &mut usize,
     ) -> anyhow::Result<()> {
         let mut stream = TcpStream::connect(config.server_address)?;
+
+        let entry = connections.vacant_entry();
+
+        *token_counter = entry.key();
     
         poll.registry()
             .register(&mut stream, Token(*token_counter), Interest::READABLE)
@@ -39,9 +43,7 @@ impl Connection {
             can_send_initial: true,
         };
     
-        connections.insert(*token_counter, connection);
-
-        *token_counter = token_counter.wrapping_add(1);
+        entry.insert(connection);
     
         Ok(())
     }
@@ -143,7 +145,10 @@ impl Connection {
 }
 
 
-pub type ConnectionMap = HashMap<usize, Connection>;
+pub type ConnectionMap = Slab<Connection>;
+
+
+const NUM_CONNECTIONS: usize = 128;
 
 
 pub fn run_socket_thread(
@@ -153,7 +158,7 @@ pub fn run_socket_thread(
 ) {
     let timeout = Duration::from_micros(config.network.poll_timeout_microseconds);
 
-    let mut connections: ConnectionMap = HashMap::new();
+    let mut connections: ConnectionMap = Slab::with_capacity(NUM_CONNECTIONS);
     let mut poll = Poll::new().expect("create poll");
     let mut events = Events::with_capacity(config.network.poll_event_capacity);
     let mut rng = SmallRng::from_entropy();
@@ -182,7 +187,7 @@ pub fn run_socket_thread(
             if event.is_readable(){
                 let token = event.token();
 
-                if let Some(connection) = connections.get_mut(&token.0){
+                if let Some(connection) = connections.get_mut(token.0){
                     connection.read_response_and_send_request(
                         config,
                         &state,
@@ -195,7 +200,7 @@ pub fn run_socket_thread(
         }
 
         if !initial_sent {
-            for connection in connections.values_mut(){
+            for (_, connection) in connections.iter_mut(){
                 if connection.can_send_initial {
                     connection.send_request(config, &state, &mut rng);
 
@@ -205,7 +210,7 @@ pub fn run_socket_thread(
         }
 
         // Slowly create new connections
-        if token_counter < 128 && iter_counter % CREATE_CONN_INTERVAL == 0 {
+        if token_counter < NUM_CONNECTIONS && iter_counter % CREATE_CONN_INTERVAL == 0 {
             Connection::create_and_register(
                 config,
                 &mut connections,