diff --git a/crates/distribution-types/src/lib.rs b/crates/distribution-types/src/lib.rs
index 88946da74..3cab4778c 100644
--- a/crates/distribution-types/src/lib.rs
+++ b/crates/distribution-types/src/lib.rs
@@ -147,7 +147,7 @@ pub enum SourceDist {
 #[derive(Debug, Clone)]
 pub struct RegistryBuiltDist {
     pub filename: WheelFilename,
-    pub file: File,
+    pub file: Box<File>,
     pub index: IndexUrl,
 }
 
@@ -172,7 +172,7 @@ pub struct PathBuiltDist {
 #[derive(Debug, Clone)]
 pub struct RegistrySourceDist {
     pub filename: SourceDistFilename,
-    pub file: File,
+    pub file: Box<File>,
     pub index: IndexUrl,
 }
 
@@ -208,14 +208,14 @@ impl Dist {
             DistFilename::WheelFilename(filename) => {
                 Self::Built(BuiltDist::Registry(RegistryBuiltDist {
                     filename,
-                    file,
+                    file: Box::new(file),
                     index,
                 }))
             }
             DistFilename::SourceDistFilename(filename) => {
                 Self::Source(SourceDist::Registry(RegistrySourceDist {
                     filename,
-                    file,
+                    file: Box::new(file),
                     index,
                 }))
             }
@@ -865,3 +865,16 @@ impl Identifier for Dist {
         }
     }
 }
+
+#[cfg(test)]
+mod test {
+    use crate::{BuiltDist, Dist, SourceDist};
+
+    /// Ensure that we don't accidentally grow the `Dist` sizes.
+    #[test]
+    fn dist_size() {
+        assert!(std::mem::size_of::<Dist>() <= 240);
+        assert!(std::mem::size_of::<BuiltDist>() <= 240);
+        assert!(std::mem::size_of::<SourceDist>() <= 168);
+    }
+}
diff --git a/crates/puffin-client/src/cached_client.rs b/crates/puffin-client/src/cached_client.rs
index 55f243c36..e4b59c80b 100644
--- a/crates/puffin-client/src/cached_client.rs
+++ b/crates/puffin-client/src/cached_client.rs
@@ -1,3 +1,4 @@
+use futures::FutureExt;
 use std::future::Future;
 use std::time::SystemTime;
 
@@ -42,14 +43,15 @@ enum CachedResponse<Payload: Serialize> {
     /// There was no prior cached response or the cache was outdated
     ///
     /// The cache policy is `None` if it isn't storable
-    ModifiedOrNew(Response, Option<CachePolicy>),
+    ModifiedOrNew(Response, Option<Box<CachePolicy>>),
 }
 
 /// Serialize the actual payload together with its caching information
 #[derive(Debug, Deserialize, Serialize)]
 pub struct DataWithCachePolicy<Payload: Serialize> {
     pub data: Payload,
-    cache_policy: CachePolicy,
+    // The cache policy is large (448 bytes at time of writing), reduce the stack size
+    cache_policy: Box<CachePolicy>,
 }
 
 /// Custom caching layer over [`reqwest::Client`] using `http-cache-semantics`.
@@ -88,7 +90,7 @@ impl CachedClient {
     /// client.
     #[instrument(skip_all)]
     pub async fn get_cached_with_callback<
-        Payload: Serialize + DeserializeOwned,
+        Payload: Serialize + DeserializeOwned + Send,
         CallBackError,
         Callback,
         CallbackReturn,
@@ -128,7 +130,7 @@ impl CachedClient {
             None
         };
 
-        let cached_response = self.send_cached(req, cached).await?;
+        let cached_response = self.send_cached(req, cached).boxed().await?;
 
         let write_cache = info_span!("write_cache", file = %cache_entry.path().display());
         match cached_response {
@@ -231,14 +233,14 @@ impl CachedClient {
                             debug!("Found not-modified response for: {url}");
                             CachedResponse::NotModified(DataWithCachePolicy {
                                 data: cached.data,
-                                cache_policy: new_policy,
+                                cache_policy: Box::new(new_policy),
                             })
                         }
                         AfterResponse::Modified(new_policy, _parts) => {
                             debug!("Found modified response for: {url}");
                             CachedResponse::ModifiedOrNew(
                                 res,
-                                new_policy.is_storable().then_some(new_policy),
+                                new_policy.is_storable().then(|| Box::new(new_policy)),
                             )
                         }
                     }
@@ -271,7 +273,7 @@ impl CachedClient {
             CachePolicy::new(&converted_req.into_parts().0, &converted_res.into_parts().0);
         Ok(CachedResponse::ModifiedOrNew(
             res,
-            cache_policy.is_storable().then_some(cache_policy),
+            cache_policy.is_storable().then(|| Box::new(cache_policy)),
         ))
     }
 }
diff --git a/crates/puffin-client/src/flat_index.rs b/crates/puffin-client/src/flat_index.rs
index b223c2f09..25a6de2a2 100644
--- a/crates/puffin-client/src/flat_index.rs
+++ b/crates/puffin-client/src/flat_index.rs
@@ -2,7 +2,7 @@ use std::collections::btree_map::Entry;
 use std::collections::BTreeMap;
 use std::path::PathBuf;
 
-use futures::StreamExt;
+use futures::{FutureExt, StreamExt};
 use reqwest::Response;
 use rustc_hash::FxHashMap;
 use tracing::{debug, info_span, instrument, warn, Instrument};
@@ -120,6 +120,7 @@ impl<'a> FlatIndexClient<'a> {
                     .collect();
                 Ok(files)
             }
+            .boxed()
             .instrument(info_span!("parse_flat_index_html", url = % url))
         };
         let files = cached_client
@@ -218,7 +219,7 @@ impl FlatIndex {
 
                 let dist = Dist::Built(BuiltDist::Registry(RegistryBuiltDist {
                     filename,
-                    file,
+                    file: Box::new(file),
                     index,
                 }));
                 match distributions.0.entry(version) {
@@ -235,7 +236,7 @@ impl FlatIndex {
             DistFilename::SourceDistFilename(filename) => {
                 let dist = Dist::Source(SourceDist::Registry(RegistrySourceDist {
                     filename: filename.clone(),
-                    file,
+                    file: Box::new(file),
                     index,
                 }));
                 match distributions.0.entry(filename.version.clone()) {
diff --git a/crates/puffin-client/src/registry_client.rs b/crates/puffin-client/src/registry_client.rs
index faf05e562..3b56c24a7 100644
--- a/crates/puffin-client/src/registry_client.rs
+++ b/crates/puffin-client/src/registry_client.rs
@@ -5,7 +5,7 @@ use std::str::FromStr;
 
 use async_http_range_reader::{AsyncHttpRangeReader, AsyncHttpRangeReaderError};
 use async_zip::tokio::read::seek::ZipFileReader;
-use futures::TryStreamExt;
+use futures::{FutureExt, TryStreamExt};
 use reqwest::{Client, ClientBuilder, Response, StatusCode};
 use reqwest_retry::policies::ExponentialBackoff;
 use reqwest_retry::RetryTransientMiddleware;
@@ -206,6 +206,7 @@ impl RegistryClient {
                     }
                 }
             }
+            .boxed()
             .instrument(info_span!("parse_simple_api", package = %package_name))
         };
         let result = self
@@ -335,6 +336,7 @@ impl RegistryClient {
                 })?;
                 Ok(metadata)
             }
+            .boxed()
             .instrument(info_span!("read_metadata_range_request", wheel = %filename))
         };
 
diff --git a/crates/puffin-distribution/src/distribution_database.rs b/crates/puffin-distribution/src/distribution_database.rs
index 75d5c36d4..309f22368 100644
--- a/crates/puffin-distribution/src/distribution_database.rs
+++ b/crates/puffin-distribution/src/distribution_database.rs
@@ -5,6 +5,7 @@ use std::str::FromStr;
 use std::sync::Arc;
 
 use fs_err::tokio as fs;
+use futures::FutureExt;
 use thiserror::Error;
 use tokio::task::JoinError;
 use tokio_util::compat::FuturesAsyncReadCompatExt;
@@ -219,7 +220,7 @@ impl<'a, Context: BuildContext + Send + Sync> DistributionDatabase<'a, Context>
                 let lock = self.locks.acquire(&dist).await;
                 let _guard = lock.lock().await;
 
-                let built_wheel = self.builder.download_and_build(source_dist).await?;
+                let built_wheel = self.builder.download_and_build(source_dist).boxed().await?;
                 Ok(LocalWheel::Built(BuiltWheel {
                     dist: dist.clone(),
                     path: built_wheel.path,
@@ -242,7 +243,9 @@ impl<'a, Context: BuildContext + Send + Sync> DistributionDatabase<'a, Context>
         dist: &Dist,
     ) -> Result<(Metadata21, Option<Url>), DistributionDatabaseError> {
         match dist {
-            Dist::Built(built_dist) => Ok((self.client.wheel_metadata(built_dist).await?, None)),
+            Dist::Built(built_dist) => {
+                Ok((self.client.wheel_metadata(built_dist).boxed().await?, None))
+            }
             Dist::Source(source_dist) => {
                 // Optimization: Skip source dist download when we must not build them anyway.
                 if self.build_context.no_build() {
@@ -263,6 +266,7 @@ impl<'a, Context: BuildContext + Send + Sync> DistributionDatabase<'a, Context>
                 let metadata = self
                     .builder
                     .download_and_build_metadata(&source_dist)
+                    .boxed()
                     .await?;
                 Ok((metadata, precise))
             }
diff --git a/crates/puffin-distribution/src/source/mod.rs b/crates/puffin-distribution/src/source/mod.rs
index 3d065b04c..e4c1b8576 100644
--- a/crates/puffin-distribution/src/source/mod.rs
+++ b/crates/puffin-distribution/src/source/mod.rs
@@ -6,7 +6,7 @@ use std::sync::Arc;
 
 use anyhow::Result;
 use fs_err::tokio as fs;
-use futures::TryStreamExt;
+use futures::{FutureExt, TryStreamExt};
 use reqwest::Response;
 use tempfile::TempDir;
 use tokio_util::compat::FuturesAsyncReadCompatExt;
@@ -96,6 +96,7 @@ impl<'a, T: BuildContext> SourceDistCachedBuilder<'a, T> {
                     &cache_shard,
                     subdirectory.as_deref(),
                 )
+                .boxed()
                 .await?
             }
             SourceDist::Registry(registry_source_dist) => {
@@ -134,6 +135,7 @@ impl<'a, T: BuildContext> SourceDistCachedBuilder<'a, T> {
                     &cache_shard,
                     None,
                 )
+                .boxed()
                 .await?
             }
             SourceDist::Git(git_source_dist) => self.git(source_dist, git_source_dist).await?,
@@ -171,6 +173,7 @@ impl<'a, T: BuildContext> SourceDistCachedBuilder<'a, T> {
                     &cache_shard,
                     subdirectory.as_deref(),
                 )
+                .boxed()
                 .await?
             }
             SourceDist::Registry(registry_source_dist) => {
@@ -189,7 +192,10 @@ impl<'a, T: BuildContext> SourceDistCachedBuilder<'a, T> {
                             path: path.clone(),
                             editable: false,
                         };
-                        return self.path_metadata(source_dist, &path_source_dist).await;
+                        return self
+                            .path_metadata(source_dist, &path_source_dist)
+                            .boxed()
+                            .await;
                     }
                 };
 
@@ -209,13 +215,18 @@ impl<'a, T: BuildContext> SourceDistCachedBuilder<'a, T> {
                     &cache_shard,
                     None,
                 )
+                .boxed()
                 .await?
             }
             SourceDist::Git(git_source_dist) => {
-                self.git_metadata(source_dist, git_source_dist).await?
+                self.git_metadata(source_dist, git_source_dist)
+                    .boxed()
+                    .await?
             }
             SourceDist::Path(path_source_dist) => {
-                self.path_metadata(source_dist, path_source_dist).await?
+                self.path_metadata(source_dist, path_source_dist)
+                    .boxed()
+                    .await?
             }
         };
 
@@ -380,6 +391,7 @@ impl<'a, T: BuildContext> SourceDistCachedBuilder<'a, T> {
         // If the backend supports `prepare_metadata_for_build_wheel`, use it.
         if let Some(metadata) = self
             .build_source_dist_metadata(source_dist, source_dist_entry.path(), subdirectory)
+            .boxed()
             .await?
         {
             if let Ok(cached) = fs::read(cache_entry.path()).await {
@@ -564,6 +576,7 @@ impl<'a, T: BuildContext> SourceDistCachedBuilder<'a, T> {
         // If the backend supports `prepare_metadata_for_build_wheel`, use it.
         if let Some(metadata) = self
             .build_source_dist_metadata(source_dist, &path_source_dist.path, None)
+            .boxed()
             .await?
         {
             // Store the metadata for this build along with all the other builds.
@@ -712,6 +725,7 @@ impl<'a, T: BuildContext> SourceDistCachedBuilder<'a, T> {
         // If the backend supports `prepare_metadata_for_build_wheel`, use it.
         if let Some(metadata) = self
             .build_source_dist_metadata(source_dist, fetch.path(), subdirectory.as_deref())
+            .boxed()
             .await?
         {
             // Store the metadata for this build along with all the other builds.
diff --git a/crates/puffin-installer/src/downloader.rs b/crates/puffin-installer/src/downloader.rs
index ca716adc8..a842cdca6 100644
--- a/crates/puffin-installer/src/downloader.rs
+++ b/crates/puffin-installer/src/downloader.rs
@@ -2,7 +2,7 @@ use std::cmp::Reverse;
 use std::path::Path;
 use std::sync::Arc;
 
-use futures::{Stream, StreamExt, TryFutureExt, TryStreamExt};
+use futures::{FutureExt, Stream, StreamExt, TryFutureExt, TryStreamExt};
 use tokio::task::JoinError;
 use tracing::{instrument, warn};
 use url::Url;
@@ -68,7 +68,7 @@ impl<'a, Context: BuildContext + Send + Sync> Downloader<'a, Context> {
     ) -> impl Stream<Item = Result<CachedDist, Error>> + 'stream {
         futures::stream::iter(distributions)
             .map(|dist| async {
-                let wheel = self.get_wheel(dist, in_flight).await?;
+                let wheel = self.get_wheel(dist, in_flight).boxed().await?;
                 if let Some(reporter) = self.reporter.as_ref() {
                     reporter.on_progress(&wheel);
                 }
@@ -158,6 +158,7 @@ impl<'a, Context: BuildContext + Send + Sync> Downloader<'a, Context> {
             let download: LocalWheel = self
                 .database
                 .get_or_build_wheel(dist.clone())
+                .boxed()
                 .map_err(|err| Error::Fetch(dist.clone(), err))
                 .await?;
             let result = Self::unzip_wheel(download).await;
diff --git a/crates/puffin-resolver/src/resolver/mod.rs b/crates/puffin-resolver/src/resolver/mod.rs
index cd5dcd193..b8ec28db0 100644
--- a/crates/puffin-resolver/src/resolver/mod.rs
+++ b/crates/puffin-resolver/src/resolver/mod.rs
@@ -683,7 +683,7 @@ impl<'a, Provider: ResolverProvider> Resolver<'a, Provider> {
     /// Fetch the metadata for a stream of packages and versions.
     async fn fetch(&self, request_stream: UnboundedReceiver<Request>) -> Result<(), ResolveError> {
         let mut response_stream = request_stream
-            .map(|request| self.process_request(request))
+            .map(|request| self.process_request(request).boxed())
             .buffer_unordered(50);
 
         while let Some(response) = response_stream.next().await {
@@ -738,6 +738,7 @@ impl<'a, Provider: ResolverProvider> Resolver<'a, Provider> {
                 let version_map = self
                     .provider
                     .get_version_map(&package_name)
+                    .boxed()
                     .await
                     .map_err(ResolveError::Client)?;
                 Ok(Some(Response::Package(package_name, version_map)))
@@ -748,6 +749,7 @@ impl<'a, Provider: ResolverProvider> Resolver<'a, Provider> {
                 let (metadata, precise) = self
                     .provider
                     .get_or_build_wheel_metadata(&dist)
+                    .boxed()
                     .await
                     .map_err(|err| match dist.clone() {
                         Dist::Built(BuiltDist::Path(built_dist)) => {
@@ -800,6 +802,7 @@ impl<'a, Provider: ResolverProvider> Resolver<'a, Provider> {
                     let (metadata, precise) = self
                         .provider
                         .get_or_build_wheel_metadata(&dist)
+                        .boxed()
                         .await
                         .map_err(|err| match dist.clone() {
                             Dist::Built(BuiltDist::Path(built_dist)) => {
diff --git a/crates/puffin-traits/src/lib.rs b/crates/puffin-traits/src/lib.rs
index ebef0c95f..3b0c51f14 100644
--- a/crates/puffin-traits/src/lib.rs
+++ b/crates/puffin-traits/src/lib.rs
@@ -51,7 +51,7 @@ use puffin_interpreter::{Interpreter, Virtualenv};
 /// them.
 
 // TODO(konstin): Proper error types
-pub trait BuildContext {
+pub trait BuildContext: Sync {
     type SourceDistBuilder: SourceBuildTrait + Send + Sync;
 
     fn cache(&self) -> &Cache;