diff --git a/Sources/SimplexArchitecture/StateContainer.swift b/Sources/SimplexArchitecture/StateContainer.swift
index 6a71187..9e6595f 100644
--- a/Sources/SimplexArchitecture/StateContainer.swift
+++ b/Sources/SimplexArchitecture/StateContainer.swift
@@ -1,8 +1,7 @@
 import Foundation
 import XCTestDynamicOverlay
 
-/// StateContainer is not thread-safe. Therefore, StateContainer must use NSLock or NSRecursiveLock for exclusions when changing values.
-/// In Store, NSRecursiveLock is used for exclusions when executing the `reduce(into:action)`.
+/// StateContainer is not thread-safe. StateContainer must be accessed from MainActor.
 @dynamicMemberLookup
 public final class StateContainer<Target: ActionSendable> {
     public var reducerState: Target.Reducer.ReducerState {
diff --git a/Sources/SimplexArchitecture/Store/Store+send.swift b/Sources/SimplexArchitecture/Store/Store+send.swift
index 7f27ad3..fd8f234 100644
--- a/Sources/SimplexArchitecture/Store/Store+send.swift
+++ b/Sources/SimplexArchitecture/Store/Store+send.swift
@@ -73,9 +73,7 @@ extension Store {
         // If Unit Testing is in progress and an action is sent from SideEffect
         if _XCTIsTesting, let effectContext = EffectContext.id {
             let before = container.copy()
-            sideEffect = withLock {
-                reduce(container, action)
-            }
+            sideEffect = reduce(container, action)
             sentFromEffectActions.append(
                 ActionTransition(
                     previous: .init(state: before.states, reducerState: before._reducerState),
@@ -86,7 +84,7 @@ extension Store {
                 )
             )
         } else {
-            sideEffect = withLock { reduce(container, action) }
+            sideEffect = reduce(container, action)
         }
 
         if case .none = sideEffect.kind {
@@ -120,13 +118,6 @@ extension Store {
         }
     }
 
-    @inlinable
-    func withLock<T>(_ operation: () throws -> T) rethrows -> T {
-        lock.lock()
-        defer { lock.unlock() }
-        return try operation()
-    }
-
     func makeSend(for container: StateContainer<Reducer.Target>) -> Send<Reducer> {
         Send(
             sendAction: { [weak self] action in
diff --git a/Sources/SimplexArchitecture/Store/Store.swift b/Sources/SimplexArchitecture/Store/Store.swift
index 01b718b..04217f6 100644
--- a/Sources/SimplexArchitecture/Store/Store.swift
+++ b/Sources/SimplexArchitecture/Store/Store.swift
@@ -16,7 +16,6 @@ public final class Store<Reducer: ReducerProtocol> {
     // Buffer to store Actions recurrently invoked through SideEffect in a single Action sent from View
     @TestOnly var sentFromEffectActions: [ActionTransition<Reducer>] = []
 
-    @usableFromInline let lock = NSRecursiveLock()
     @usableFromInline var pullbackAction: ((Reducer.Action) -> Void)?
     @usableFromInline var pullbackReducerAction: ((Reducer.ReducerAction) -> Void)?