diff --git a/Framework/Core/include/Framework/DataProcessingContext.h b/Framework/Core/include/Framework/DataProcessingContext.h
index 221f7b099dc07..f66f7d7c7f8d2 100644
--- a/Framework/Core/include/Framework/DataProcessingContext.h
+++ b/Framework/Core/include/Framework/DataProcessingContext.h
@@ -13,6 +13,7 @@
 
 #include "Framework/DataRelayer.h"
 #include "Framework/AlgorithmSpec.h"
+#include <atomic>
 #include <functional>
 
 namespace o2::framework
@@ -33,7 +34,7 @@ struct DataProcessorContext {
   DataProcessorContext(DataProcessorContext const&) = delete;
   DataProcessorContext() = default;
 
-  bool allDone = false;
+  std::atomic<bool> allDone = false;
   /// Latest run number we processed globally for this DataProcessor.
   int64_t lastRunNumberProcessed = -1;
 
@@ -43,7 +44,6 @@ struct DataProcessorContext {
 
   // FIXME: move stuff here from the list below... ;-)
   ServiceRegistry* registry = nullptr;
-  std::vector<DataRelayer::RecordAction> completed;
   std::vector<ExpirationHandler> expirationHandlers;
   AlgorithmSpec::InitCallback init;
   AlgorithmSpec::ProcessCallback statefulProcess;
diff --git a/Framework/Core/include/Framework/StreamContext.h b/Framework/Core/include/Framework/StreamContext.h
index 79c8ad798836a..fb29c3e164aef 100644
--- a/Framework/Core/include/Framework/StreamContext.h
+++ b/Framework/Core/include/Framework/StreamContext.h
@@ -11,6 +11,7 @@
 #ifndef O2_FRAMEWORK_STREAMCONTEXT_H_
 #define O2_FRAMEWORK_STREAMCONTEXT_H_
 
+#include "Framework/DataRelayer.h"
 #include "Framework/ServiceHandle.h"
 #include "ProcessingContext.h"
 #include "ServiceSpec.h"
@@ -64,6 +65,10 @@ struct StreamContext {
   // the callback will be called for all of them.
   std::vector<ServiceStartStreamHandle> preStartStreamHandles;
 
+  /// Per-stream list of actions ready to be dispatched. Populated by
+  /// getReadyToProcess() and consumed by tryDispatchComputation().
+  std::vector<DataRelayer::RecordAction> completed;
+
   // Information on wether or not all the required routes have been created.
   // This is used to check if the LifetimeTimeframe routes were all created
   // for a given iteration.
diff --git a/Framework/Core/src/DataProcessingDevice.cxx b/Framework/Core/src/DataProcessingDevice.cxx
index be25133158072..ee68d0728d52e 100644
--- a/Framework/Core/src/DataProcessingDevice.cxx
+++ b/Framework/Core/src/DataProcessingDevice.cxx
@@ -187,9 +187,13 @@ DataProcessingDevice::DataProcessingDevice(RunningDeviceRef running, ServiceRegi
   // 99 is to execute DPL callbacks last
   this->SubscribeToStateChange("99-dpl", stateWatcher);
 
-  // One task for now.
-  mStreams.resize(1);
-  mHandles.resize(1);
+  auto* poolSizeEnv = getenv("DPL_THREADPOOL_SIZE");
+  // 0 (or unset): synchronous execution on the main thread.
+  // N > 0: N concurrent async streams; I/O runs on the main thread while
+  //        computation runs on N pool threads.
+  size_t numStreams = poolSizeEnv ? std::max(0, std::atoi(poolSizeEnv)) : 0;
+  mStreams.resize(std::max(numStreams, 1UL));
+  mHandles.resize(std::max(numStreams, 1UL));
 
   ServiceRegistryRef ref{mServiceRegistry};
 
@@ -1210,10 +1214,8 @@ void DataProcessingDevice::Run()
   O2_SIGNPOST_ID_FROM_POINTER(lid, device, state.loop);
   O2_SIGNPOST_START(device, lid, "device_state", "First iteration of the device loop");
 
-  bool dplEnableMultithreding = getenv("DPL_THREADPOOL_SIZE") != nullptr;
-  if (dplEnableMultithreding) {
-    setenv("UV_THREADPOOL_SIZE", "1", 1);
-  }
+  auto* poolSizeEnv = getenv("DPL_THREADPOOL_SIZE");
+  bool dplEnableMultithreding = poolSizeEnv && std::atoi(poolSizeEnv) > 0;
 
   while (state.transitionHandling != TransitionHandlingState::Expired) {
     if (state.nextFairMQState.empty() == false) {
@@ -1634,6 +1636,7 @@ void DataProcessingDevice::doPrepare(ServiceRegistryRef ref)
 void DataProcessingDevice::doRun(ServiceRegistryRef ref)
 {
   auto& context = ref.get<DataProcessorContext>();
+  auto& streamContext = ref.get<StreamContext>();
   O2_SIGNPOST_ID_FROM_POINTER(dpid, device, &context);
   auto& state = ref.get<DeviceState>();
   auto& spec = ref.get<DeviceSpec const>();
@@ -1642,9 +1645,9 @@ void DataProcessingDevice::doRun(ServiceRegistryRef ref)
     return;
   }
 
-  context.completed.clear();
-  context.completed.reserve(16);
-  if (DataProcessingDevice::tryDispatchComputation(ref, context.completed)) {
+  streamContext.completed.clear();
+  streamContext.completed.reserve(16);
+  if (DataProcessingDevice::tryDispatchComputation(ref, streamContext.completed)) {
     state.lastActiveDataProcessor.store(&context);
   }
   DanglingContext danglingContext{*context.registry};
@@ -1658,8 +1661,8 @@ void DataProcessingDevice::doRun(ServiceRegistryRef ref)
     state.lastActiveDataProcessor = &context;
   }
 
-  context.completed.clear();
-  if (DataProcessingDevice::tryDispatchComputation(ref, context.completed)) {
+  streamContext.completed.clear();
+  if (DataProcessingDevice::tryDispatchComputation(ref, streamContext.completed)) {
     state.lastActiveDataProcessor = &context;
   }
 
@@ -1685,7 +1688,7 @@ void DataProcessingDevice::doRun(ServiceRegistryRef ref)
 
     bool shouldProcess = DataProcessingHelpers::hasOnlyGenerated(spec) == false;
 
-    while (DataProcessingDevice::tryDispatchComputation(ref, context.completed) && shouldProcess) {
+    while (DataProcessingDevice::tryDispatchComputation(ref, streamContext.completed) && shouldProcess) {
       relayer.processDanglingInputs(context.expirationHandlers, *context.registry, false);
     }