ref(projects): Prefetch sampling project

relay-server/src/endpoints/common.rs

@@ -371,9 +371,20 @@ pub async fn handle_envelope(
         return Ok(event_id);
     }
 
+    let project_key = managed_envelope.envelope().meta().public_key();
+
+    // Prefetch sampling project key, current spooling implementations rely on this behavior.
+    //
+    // To be changed once spool v1 has been removed.
+    if let Some(sampling_project_key) = managed_envelope.envelope().sampling_key() {
+        if sampling_project_key != project_key {
+            state.project_cache_handle().fetch(sampling_project_key);
+        }
+    }
+
     let checked = state
         .project_cache_handle()
-        .get(managed_envelope.scoping().project_key)
+        .get(project_key)
         .check_envelope(managed_envelope)
         .map_err(BadStoreRequest::EventRejected)?;
 

relay-server/src/services/buffer/mod.rs

@@ -274,6 +274,7 @@ impl EnvelopeBufferService {
                 // avoid flooding the project cache with `UpdateProject` messages.
                 if Instant::now() >= next_project_fetch {
                     relay_log::trace!("EnvelopeBufferService: requesting project(s) update");
+
                     let ProjectKeyPair {
                         own_key,
                         sampling_key,