diff --git a/pkg/runtime/node/build.go b/pkg/runtime/node/build.go
index a52b6a3f3..1cf6a771c 100644
--- a/pkg/runtime/node/build.go
+++ b/pkg/runtime/node/build.go
@@ -23,8 +23,8 @@ var forceExternal = []string{
 }
 
 func (r *Runtime) Build(ctx context.Context, input *runtime.BuildInput) (*runtime.BuildOutput, error) {
-	r.lock.Acquire(ctx, 1)
-	defer r.lock.Release(1)
+	r.concurrency.Acquire(ctx, 1)
+	defer r.concurrency.Release(1)
 	var properties NodeProperties
 	json.Unmarshal(input.Properties, &properties)
 
@@ -132,14 +132,14 @@ func (r *Runtime) Build(ctx context.Context, input *runtime.BuildInput) (*runtim
 		options.Target = properties.ESBuild.Target
 	}
 
-	buildContext, ok := r.contexts[input.FunctionID]
+	buildContext, ok := r.contexts.Load(input.FunctionID)
 	if !ok {
 		buildContext, _ = esbuild.Context(options)
-		r.contexts[input.FunctionID] = buildContext
+		r.contexts.Store(input.FunctionID, buildContext)
 	}
 
-	result := buildContext.Rebuild()
-	r.results[input.FunctionID] = result
+	result := buildContext.(esbuild.BuildContext).Rebuild()
+	r.results.Store(input.FunctionID, result)
 	errors := []string{}
 	for _, error := range result.Errors {
 		text := error.Text
diff --git a/pkg/runtime/node/node.go b/pkg/runtime/node/node.go
index 625370ba1..a9a36c4ab 100644
--- a/pkg/runtime/node/node.go
+++ b/pkg/runtime/node/node.go
@@ -58,10 +58,10 @@ var LoaderToString = []string{
 }
 
 type Runtime struct {
-	cfgPath  string
-	contexts map[string]esbuild.BuildContext
-	results  map[string]esbuild.BuildResult
-	lock     *semaphore.Weighted
+	cfgPath     string
+	contexts    sync.Map
+	results     sync.Map
+	concurrency *semaphore.Weighted
 }
 
 func New() *Runtime {
@@ -70,9 +70,9 @@ func New() *Runtime {
 		weight, _ = strconv.ParseInt(flag.SST_BUILD_CONCURRENCY, 10, 64)
 	}
 	return &Runtime{
-		contexts: map[string]esbuild.BuildContext{},
-		results:  map[string]esbuild.BuildResult{},
-		lock:     semaphore.NewWeighted(weight),
+		contexts:    sync.Map{},
+		results:     sync.Map{},
+		concurrency: semaphore.NewWeighted(weight),
 	}
 }