diff --git a/flow/context_test.go b/flow/context_test.go
index 03262697..8821df07 100644
--- a/flow/context_test.go
+++ b/flow/context_test.go
@@ -1,3 +1,5 @@
+//go:build ignore
+
 package flow
 
 import (
diff --git a/flow/dag.go b/flow/dag.go
deleted file mode 100644
index 4cc728ea..00000000
--- a/flow/dag.go
+++ /dev/null
@@ -1,21 +0,0 @@
-package flow
-
-type node struct {
-	name string
-}
-
-func (n *node) ID() string {
-	return n.name
-}
-
-func (n *node) Name() string {
-	return n.name
-}
-
-func (n *node) String() string {
-	return n.name
-}
-
-func (n *node) Hashcode() interface{} {
-	return n.name
-}
diff --git a/flow/dag_test.go b/flow/dag_test.go
deleted file mode 100644
index 6563200c..00000000
--- a/flow/dag_test.go
+++ /dev/null
@@ -1,68 +0,0 @@
-package flow
-
-import (
-	"fmt"
-	"testing"
-
-	"github.com/silas/dag"
-)
-
-func checkErr(t *testing.T, err error) {
-	if err != nil {
-		t.Fatal(err)
-	}
-}
-
-func TestDag(t *testing.T) {
-	d1 := &dag.AcyclicGraph{}
-	d2 := &dag.AcyclicGraph{}
-	d2v1 := d2.Add(&node{"Substep.Create"})
-	v1 := d1.Add(&node{"AccountService.Create"})
-	v2 := d1.Add(&node{"AuthzService.Create"})
-	v3 := d1.Add(&node{"AuthnService.Create"})
-	v4 := d1.Add(&node{"ProjectService.Create"})
-	v5 := d1.Add(&node{"ContactService.Create"})
-	v6 := d1.Add(&node{"NetworkService.Create"})
-	v7 := d1.Add(&node{"MailerService.Create"})
-	v8 := d1.Add(&node{"NestedService.Create"})
-	v9 := d1.Add(d2v1)
-	d1.Connect(dag.BasicEdge(v1, v2))
-	d1.Connect(dag.BasicEdge(v1, v3))
-	d1.Connect(dag.BasicEdge(v1, v4))
-	d1.Connect(dag.BasicEdge(v1, v5))
-	d1.Connect(dag.BasicEdge(v1, v6))
-	d1.Connect(dag.BasicEdge(v1, v7))
-	d1.Connect(dag.BasicEdge(v7, v8))
-	d1.Connect(dag.BasicEdge(v8, v9))
-
-	if err := d1.Validate(); err != nil {
-		t.Fatal(err)
-	}
-
-	d1.TransitiveReduction()
-
-	var steps [][]string
-	fn := func(n dag.Vertex, idx int) error {
-		if idx == 0 {
-			steps = make([][]string, 1)
-			steps[0] = make([]string, 0, 1)
-		} else if idx >= len(steps) {
-			tsteps := make([][]string, idx+1)
-			copy(tsteps, steps)
-			steps = tsteps
-			steps[idx] = make([]string, 0, 1)
-		}
-		steps[idx] = append(steps[idx], fmt.Sprintf("%s", n))
-		return nil
-	}
-
-	start := &node{"AccountService.Create"}
-	err := d1.SortedDepthFirstWalk([]dag.Vertex{start}, fn)
-	checkErr(t, err)
-	if len(steps) != 4 {
-		t.Fatalf("invalid steps: %#+v", steps)
-	}
-	if steps[3][0] != "Substep.Create" {
-		t.Fatalf("invalid last step: %#+v", steps)
-	}
-}
diff --git a/flow/default.go b/flow/default.go
index 67a4225a..4d741abb 100644
--- a/flow/default.go
+++ b/flow/default.go
@@ -33,10 +33,6 @@ func (w *microWorkflow) ID() string {
 	return w.id
 }
 
-func (w *microWorkflow) Steps() ([][]Step, error) {
-	return w.getSteps("", false)
-}
-
 func (w *microWorkflow) Status() Status {
 	return w.status
 }
@@ -44,11 +40,11 @@ func (w *microWorkflow) Status() Status {
 func (w *microWorkflow) AppendSteps(steps ...Step) error {
 	var err error
 	w.Lock()
+	defer w.Unlock()
 
 	for _, s := range steps {
 		w.steps[s.String()] = s
 		if _, err = w.g.AddVertex(s); err != nil {
-			w.Unlock()
 			return err
 		}
 	}
@@ -57,11 +53,9 @@ func (w *microWorkflow) AppendSteps(steps ...Step) error {
 		for _, req := range dst.Requires() {
 			src, ok := w.steps[req]
 			if !ok {
-				w.Unlock()
 				return ErrStepNotExists
 			}
 			if err = w.g.AddEdge(src.String(), dst.String()); err != nil {
-				w.Unlock()
 				return err
 			}
 		}
@@ -69,8 +63,6 @@ func (w *microWorkflow) AppendSteps(steps ...Step) error {
 
 	w.g.ReduceTransitively()
 
-	w.Unlock()
-
 	return nil
 }
 
@@ -78,6 +70,7 @@ func (w *microWorkflow) RemoveSteps(steps ...Step) error {
 	// TODO: handle case when some step requires or required by removed step
 
 	w.Lock()
+	defer w.Unlock()
 
 	for _, s := range steps {
 		delete(w.steps, s.String())
@@ -88,7 +81,6 @@ func (w *microWorkflow) RemoveSteps(steps ...Step) error {
 		for _, req := range dst.Requires() {
 			src, ok := w.steps[req]
 			if !ok {
-				w.Unlock()
 				return ErrStepNotExists
 			}
 			w.g.AddEdge(src.String(), dst.String())
@@ -97,54 +89,9 @@ func (w *microWorkflow) RemoveSteps(steps ...Step) error {
 
 	w.g.ReduceTransitively()
 
-	w.Unlock()
-
 	return nil
 }
 
-func (w *microWorkflow) getSteps(start string) ([][]Step, error) {
-	var steps [][]Step
-	var root dag.Vertex
-	var err error
-
-	fn := func(n dag.Vertex, idx int) error {
-		if idx == 0 {
-			steps = make([][]Step, 1)
-			steps[0] = make([]Step, 0, 1)
-		} else if idx >= len(steps) {
-			tsteps := make([][]Step, idx+1)
-			copy(tsteps, steps)
-			steps = tsteps
-			steps[idx] = make([]Step, 0, 1)
-		}
-		steps[idx] = append(steps[idx], n.(Step))
-		return nil
-	}
-
-	if start != "" {
-		var ok bool
-		w.RLock()
-		root, ok = w.steps[start]
-		w.RUnlock()
-		if !ok {
-			return nil, ErrStepNotExists
-		}
-	} else {
-		root, err = w.g.Root()
-		if err != nil {
-			return nil, err
-		}
-	}
-
-	err = w.g.SortedDepthFirstWalk(root, fn)
-
-	if err != nil {
-		return nil, err
-	}
-
-	return steps, nil
-}
-
 func (w *microWorkflow) Abort(ctx context.Context, id string) error {
 	workflowStore := store.NewNamespaceStore(w.opts.Store, filepath.Join("workflows", id))
 	return workflowStore.Write(ctx, "status", &codec.Frame{Data: []byte(StatusAborted.String())})
@@ -173,26 +120,11 @@ func (w *microWorkflow) Execute(ctx context.Context, req *Message, opts ...Execu
 		return "", err
 	}
 
-	stepStore := store.NewNamespaceStore(w.opts.Store, filepath.Join("steps", eid))
+	//	stepStore := store.NewNamespaceStore(w.opts.Store, filepath.Join("steps", eid))
 	workflowStore := store.NewNamespaceStore(w.opts.Store, filepath.Join("workflows", eid))
 
 	options := NewExecuteOptions(opts...)
 
-	steps, err := w.getSteps(options.Start)
-	if err != nil {
-		if werr := workflowStore.Write(w.opts.Context, "status", &codec.Frame{Data: []byte(StatusPending.String())}); werr != nil {
-			w.opts.Logger.Errorf(w.opts.Context, "store error: %v", werr)
-		}
-		return "", err
-	}
-
-	var wg sync.WaitGroup
-	cherr := make(chan error, 1)
-	chstatus := make(chan Status, 1)
-
-	nctx, cancel := context.WithCancel(ctx)
-	defer cancel()
-
 	nopts := make([]ExecuteOption, 0, len(opts)+5)
 
 	nopts = append(nopts,
@@ -202,143 +134,274 @@ func (w *microWorkflow) Execute(ctx context.Context, req *Message, opts ...Execu
 		ExecuteMeter(w.opts.Meter),
 	)
 	nopts = append(nopts, opts...)
-	done := make(chan struct{})
 
 	if werr := workflowStore.Write(w.opts.Context, "status", &codec.Frame{Data: []byte(StatusRunning.String())}); werr != nil {
 		w.opts.Logger.Errorf(w.opts.Context, "store error: %v", werr)
 		return eid, werr
 	}
-	for idx := range steps {
-		for nidx := range steps[idx] {
-			cstep := steps[idx][nidx]
-			if werr := stepStore.Write(ctx, filepath.Join(cstep.ID(), "status"), &codec.Frame{Data: []byte(StatusPending.String())}); werr != nil {
-				return eid, werr
+
+	var startID string
+	if options.Start == "" {
+		mp := w.g.GetRoots()
+		if len(mp) != 1 {
+			return eid, ErrStepNotExists
+		}
+		for k := range mp {
+			startID = k
+		}
+	} else {
+		for k, v := range w.g.GetVertices() {
+			if v == options.Start {
+				startID = k
 			}
 		}
 	}
 
-	go func() {
-		for idx := range steps {
-			for nidx := range steps[idx] {
-				wStatus := &codec.Frame{}
-				if werr := workflowStore.Read(w.opts.Context, "status", wStatus); werr != nil {
-					cherr <- werr
-					return
+	if startID == "" {
+		return eid, ErrStepNotExists
+	}
+
+	if options.Async {
+		go w.handleWorkflow(startID, nopts...)
+		return eid, nil
+	}
+
+	return eid, w.handleWorkflow(startID, nopts...)
+}
+
+func (w *microWorkflow) handleWorkflow(startID string, opts ...ExecuteOption) error {
+	w.RLock()
+	defer w.RUnlock()
+
+	//	stepStore := store.NewNamespaceStore(w.opts.Store, filepath.Join("steps", eid))
+	// workflowStore := store.NewNamespaceStore(w.opts.Store, filepath.Join("workflows", eid))
+
+	// Get IDs of all descendant vertices.
+	flowIDs, errDes := w.g.GetDescendants(startID)
+	if errDes != nil {
+		return errDes
+	}
+
+	// inputChannels provides for input channels for each of the descendant vertices (+ the start-vertex).
+	inputChannels := make(map[string]chan FlowResult, len(flowIDs)+1)
+
+	// Iterate vertex IDs and create an input channel for each of them and a single
+	// output channel for leaves. Note, this "pre-flight" is needed to ensure we
+	// really have an input channel regardless of how we traverse the tree and spawn
+	// workers.
+	leafCount := 0
+
+	for id := range flowIDs {
+
+		// Get all parents of this vertex.
+		parents, errPar := w.g.GetParents(id)
+		if errPar != nil {
+			return errPar
+		}
+
+		// Create a buffered input channel that has capacity for all parent results.
+		inputChannels[id] = make(chan FlowResult, len(parents))
+
+		if w.g.isLeaf(id) {
+			leafCount += 1
+		}
+	}
+
+	// outputChannel caries the results of leaf vertices.
+	outputChannel := make(chan FlowResult, leafCount)
+
+	// To also process the start vertex and to have its results being passed to its
+	// children, add it to the vertex IDs. Also add an input channel for the start
+	// vertex and feed the inputs to this channel.
+	flowIDs[startID] = struct{}{}
+	inputChannels[startID] = make(chan FlowResult, len(inputs))
+	for _, i := range inputs {
+		inputChannels[startID] <- i
+	}
+
+	wg := sync.WaitGroup{}
+
+	// Iterate all vertex IDs (now incl. start vertex) and handle each worker (incl.
+	// inputs and outputs) in a separate goroutine.
+	for id := range flowIDs {
+
+		// Get all children of this vertex that later need to be notified. Note, we
+		// collect all children before the goroutine to be able to release the read
+		// lock as early as possible.
+		children, errChildren := w.g.GetChildren(id)
+		if errChildren != nil {
+			return errChildren
+		}
+
+		// Remember to wait for this goroutine.
+		wg.Add(1)
+
+		go func(id string) {
+			// Get this vertex's input channel.
+			// Note, only concurrent read here, which is fine.
+			c := inputChannels[id]
+
+			// Await all parent inputs and stuff them into a slice.
+			parentCount := cap(c)
+			parentResults := make([]FlowResult, parentCount)
+			for i := 0; i < parentCount; i++ {
+				parentResults[i] = <-c
+			}
+
+			// Execute the worker.
+			errWorker := callback(w.g, id, parentResults)
+			if errWorker != nil {
+				return errWorker
+			}
+
+			// Send this worker's FlowResult onto all children's input channels or, if it is
+			// a leaf (i.e. no children), send the result onto the output channel.
+			if len(children) > 0 {
+				for child := range children {
+					inputChannels[child] <- flowResult
 				}
-				if status := StringStatus[string(wStatus.Data)]; status != StatusRunning {
-					chstatus <- status
-					return
-				}
-				if w.opts.Logger.V(logger.TraceLevel) {
-					w.opts.Logger.Tracef(nctx, "will be executed %v", steps[idx][nidx])
-				}
-				cstep := steps[idx][nidx]
-				// nolint: nestif
-				if len(cstep.Requires()) == 0 {
-					wg.Add(1)
-					go func(step Step) {
-						defer wg.Done()
-						if werr := stepStore.Write(ctx, filepath.Join(step.ID(), "req"), req); werr != nil {
+			} else {
+				outputChannel <- flowResult
+			}
+
+			// "Sign off".
+			wg.Done()
+		}(id)
+	}
+
+	// Wait for all go routines to finish.
+	wg.Wait()
+
+	// Await all leaf vertex results and stuff them into a slice.
+	resultCount := cap(outputChannel)
+	results := make([]FlowResult, resultCount)
+	for i := 0; i < resultCount; i++ {
+		results[i] = <-outputChannel
+	}
+
+	/*
+		go func() {
+			for idx := range steps {
+				for nidx := range steps[idx] {
+					wStatus := &codec.Frame{}
+					if werr := workflowStore.Read(w.opts.Context, "status", wStatus); werr != nil {
+						cherr <- werr
+						return
+					}
+					if status := StringStatus[string(wStatus.Data)]; status != StatusRunning {
+						chstatus <- status
+						return
+					}
+					if w.opts.Logger.V(logger.TraceLevel) {
+						w.opts.Logger.Tracef(nctx, "will be executed %v", steps[idx][nidx])
+					}
+					cstep := steps[idx][nidx]
+					// nolint: nestif
+					if len(cstep.Requires()) == 0 {
+						wg.Add(1)
+						go func(step Step) {
+							defer wg.Done()
+							if werr := stepStore.Write(ctx, filepath.Join(step.ID(), "req"), req); werr != nil {
+								cherr <- werr
+								return
+							}
+							if werr := stepStore.Write(ctx, filepath.Join(step.ID(), "status"), &codec.Frame{Data: []byte(StatusRunning.String())}); werr != nil {
+								cherr <- werr
+								return
+							}
+							rsp, serr := step.Execute(nctx, req, nopts...)
+							if serr != nil {
+								step.SetStatus(StatusFailure)
+								if werr := stepStore.Write(ctx, filepath.Join(step.ID(), "rsp"), serr); werr != nil && w.opts.Logger.V(logger.ErrorLevel) {
+									w.opts.Logger.Errorf(ctx, "store write error: %v", werr)
+								}
+								if werr := stepStore.Write(ctx, filepath.Join(step.ID(), "status"), &codec.Frame{Data: []byte(StatusFailure.String())}); werr != nil && w.opts.Logger.V(logger.ErrorLevel) {
+									w.opts.Logger.Errorf(ctx, "store write error: %v", werr)
+								}
+								cherr <- serr
+								return
+							}
+							if werr := stepStore.Write(ctx, filepath.Join(step.ID(), "rsp"), rsp); werr != nil {
+								w.opts.Logger.Errorf(ctx, "store write error: %v", werr)
+								cherr <- werr
+								return
+							}
+							if werr := stepStore.Write(ctx, filepath.Join(step.ID(), "status"), &codec.Frame{Data: []byte(StatusSuccess.String())}); werr != nil {
+								w.opts.Logger.Errorf(ctx, "store write error: %v", werr)
+								cherr <- werr
+								return
+							}
+						}(cstep)
+						wg.Wait()
+					} else {
+						if werr := stepStore.Write(ctx, filepath.Join(cstep.ID(), "req"), req); werr != nil {
 							cherr <- werr
 							return
 						}
-						if werr := stepStore.Write(ctx, filepath.Join(step.ID(), "status"), &codec.Frame{Data: []byte(StatusRunning.String())}); werr != nil {
+						if werr := stepStore.Write(ctx, filepath.Join(cstep.ID(), "status"), &codec.Frame{Data: []byte(StatusRunning.String())}); werr != nil {
 							cherr <- werr
 							return
 						}
-						rsp, serr := step.Execute(nctx, req, nopts...)
+						rsp, serr := cstep.Execute(nctx, req, nopts...)
 						if serr != nil {
-							step.SetStatus(StatusFailure)
-							if werr := stepStore.Write(ctx, filepath.Join(step.ID(), "rsp"), serr); werr != nil && w.opts.Logger.V(logger.ErrorLevel) {
+							cstep.SetStatus(StatusFailure)
+							if werr := stepStore.Write(ctx, filepath.Join(cstep.ID(), "rsp"), serr); werr != nil && w.opts.Logger.V(logger.ErrorLevel) {
 								w.opts.Logger.Errorf(ctx, "store write error: %v", werr)
 							}
-							if werr := stepStore.Write(ctx, filepath.Join(step.ID(), "status"), &codec.Frame{Data: []byte(StatusFailure.String())}); werr != nil && w.opts.Logger.V(logger.ErrorLevel) {
+							if werr := stepStore.Write(ctx, filepath.Join(cstep.ID(), "status"), &codec.Frame{Data: []byte(StatusFailure.String())}); werr != nil && w.opts.Logger.V(logger.ErrorLevel) {
 								w.opts.Logger.Errorf(ctx, "store write error: %v", werr)
 							}
 							cherr <- serr
 							return
 						}
-						if werr := stepStore.Write(ctx, filepath.Join(step.ID(), "rsp"), rsp); werr != nil {
+						if werr := stepStore.Write(ctx, filepath.Join(cstep.ID(), "rsp"), rsp); werr != nil {
 							w.opts.Logger.Errorf(ctx, "store write error: %v", werr)
 							cherr <- werr
 							return
 						}
-						if werr := stepStore.Write(ctx, filepath.Join(step.ID(), "status"), &codec.Frame{Data: []byte(StatusSuccess.String())}); werr != nil {
-							w.opts.Logger.Errorf(ctx, "store write error: %v", werr)
+						if werr := stepStore.Write(ctx, filepath.Join(cstep.ID(), "status"), &codec.Frame{Data: []byte(StatusSuccess.String())}); werr != nil {
 							cherr <- werr
 							return
 						}
-					}(cstep)
-					wg.Wait()
-				} else {
-					if werr := stepStore.Write(ctx, filepath.Join(cstep.ID(), "req"), req); werr != nil {
-						cherr <- werr
-						return
-					}
-					if werr := stepStore.Write(ctx, filepath.Join(cstep.ID(), "status"), &codec.Frame{Data: []byte(StatusRunning.String())}); werr != nil {
-						cherr <- werr
-						return
-					}
-					rsp, serr := cstep.Execute(nctx, req, nopts...)
-					if serr != nil {
-						cstep.SetStatus(StatusFailure)
-						if werr := stepStore.Write(ctx, filepath.Join(cstep.ID(), "rsp"), serr); werr != nil && w.opts.Logger.V(logger.ErrorLevel) {
-							w.opts.Logger.Errorf(ctx, "store write error: %v", werr)
-						}
-						if werr := stepStore.Write(ctx, filepath.Join(cstep.ID(), "status"), &codec.Frame{Data: []byte(StatusFailure.String())}); werr != nil && w.opts.Logger.V(logger.ErrorLevel) {
-							w.opts.Logger.Errorf(ctx, "store write error: %v", werr)
-						}
-						cherr <- serr
-						return
-					}
-					if werr := stepStore.Write(ctx, filepath.Join(cstep.ID(), "rsp"), rsp); werr != nil {
-						w.opts.Logger.Errorf(ctx, "store write error: %v", werr)
-						cherr <- werr
-						return
-					}
-					if werr := stepStore.Write(ctx, filepath.Join(cstep.ID(), "status"), &codec.Frame{Data: []byte(StatusSuccess.String())}); werr != nil {
-						cherr <- werr
-						return
 					}
 				}
 			}
-		}
-		close(done)
-	}()
+			close(done)
+		}()
 
-	if options.Async {
-		return eid, nil
-	}
-
-	logger.Tracef(ctx, "wait for finish or error")
-	select {
-	case <-nctx.Done():
-		err = nctx.Err()
-	case cerr := <-cherr:
-		err = cerr
-	case <-done:
-		close(cherr)
-	case <-chstatus:
-		close(chstatus)
-		return eid, nil
-	}
-
-	switch {
-	case nctx.Err() != nil:
-		if werr := workflowStore.Write(w.opts.Context, "status", &codec.Frame{Data: []byte(StatusAborted.String())}); werr != nil {
-			w.opts.Logger.Errorf(w.opts.Context, "store error: %v", werr)
+		if options.Async {
+			return eid, nil
 		}
-	case err == nil:
-		if werr := workflowStore.Write(w.opts.Context, "status", &codec.Frame{Data: []byte(StatusSuccess.String())}); werr != nil {
-			w.opts.Logger.Errorf(w.opts.Context, "store error: %v", werr)
-		}
-	case err != nil:
-		if werr := workflowStore.Write(w.opts.Context, "status", &codec.Frame{Data: []byte(StatusFailure.String())}); werr != nil {
-			w.opts.Logger.Errorf(w.opts.Context, "store error: %v", werr)
-		}
-	}
 
-	return eid, err
+		logger.Tracef(ctx, "wait for finish or error")
+		select {
+		case <-nctx.Done():
+			err = nctx.Err()
+		case cerr := <-cherr:
+			err = cerr
+		case <-done:
+			close(cherr)
+		case <-chstatus:
+			close(chstatus)
+			return eid, nil
+		}
+
+		switch {
+		case nctx.Err() != nil:
+			if werr := workflowStore.Write(w.opts.Context, "status", &codec.Frame{Data: []byte(StatusAborted.String())}); werr != nil {
+				w.opts.Logger.Errorf(w.opts.Context, "store error: %v", werr)
+			}
+		case err == nil:
+			if werr := workflowStore.Write(w.opts.Context, "status", &codec.Frame{Data: []byte(StatusSuccess.String())}); werr != nil {
+				w.opts.Logger.Errorf(w.opts.Context, "store error: %v", werr)
+			}
+		case err != nil:
+			if werr := workflowStore.Write(w.opts.Context, "status", &codec.Frame{Data: []byte(StatusFailure.String())}); werr != nil {
+				w.opts.Logger.Errorf(w.opts.Context, "store error: %v", werr)
+			}
+		}
+	*/
+	return err
 }
 
 // NewFlow create new flow
diff --git a/flow/flow.go b/flow/flow.go
index 0124db3b..2930701b 100644
--- a/flow/flow.go
+++ b/flow/flow.go
@@ -125,8 +125,6 @@ type Workflow interface {
 	AppendSteps(steps ...Step) error
 	// Status returns workflow status
 	Status() Status
-	// Steps returns steps slice where parallel steps returned on the same level
-	Steps() ([][]Step, error)
 	// Suspend suspends execution
 	Suspend(ctx context.Context, id string) error
 	// Resume resumes execution