diff --git a/web/database/types/comm-query-executor.js b/web/database/types/comm-query-executor.js
new file mode 100644
--- /dev/null
+++ b/web/database/types/comm-query-executor.js
@@ -0,0 +1,7 @@
+// @flow
+
+declare export class CommQueryExecutor {
+  static testDBOperation: () => string;
+}
+
+export type CommQueryExecutorType = typeof CommQueryExecutor;
diff --git a/web/database/types/module.js b/web/database/types/module.js
new file mode 100644
--- /dev/null
+++ b/web/database/types/module.js
@@ -0,0 +1,70 @@
+// @flow
+
+import type { CommQueryExecutorType } from './comm-query-executor.js';
+import type { FS } from './file-system.js';
+
+interface WebAssembly$Module {}
+
+type Emscripten$EnvironmentType = 'WEB' | 'NODE' | 'SHELL' | 'WORKER';
+
+type Emscripten$WebAssemblyImports = $ReadOnlyArray<{
+  +name: string,
+  +kind: string,
+}>;
+
+type Emscripten$WebAssemblyExports = $ReadOnlyArray<{
+  +module: string,
+  +name: string,
+  +kind: string,
+}>;
+
+declare export class EmscriptenModule {
+  print(str: string): void;
+  printErr(str: string): void;
+  arguments: string[];
+  environment: Emscripten$EnvironmentType;
+  preInit: () => void | $ReadOnlyArray<() => void>;
+  preRun: $ReadOnlyArray<() => void>;
+  postRun: () => void | $ReadOnlyArray<() => void>;
+  onAbort: {
+    (what: mixed): void,
+  };
+  onRuntimeInitialized: () => void;
+  preinitializedWebGLContext: WebGLRenderingContext;
+  noInitialRun: boolean;
+  noExitRuntime: boolean;
+  logReadFiles: boolean;
+  filePackagePrefixURL: string;
+  wasmBinary: ArrayBuffer;
+  destroy(object: { +[key: string]: mixed }): void;
+  getPreloadedPackage(
+    remotePackageName: string,
+    remotePackageSize: number,
+  ): ArrayBuffer;
+  instantiateWasm(
+    imports: Emscripten$WebAssemblyImports,
+    successCallback: (module: WebAssembly$Module) => void,
+  ): Emscripten$WebAssemblyExports;
+  locateFile(url: string, scriptDirectory?: string): string;
+  onCustomMessage(event: MessageEvent): void;
+  HEAP: Int32Array;
+  IHEAP: Int32Array;
+  FHEAP: Float64Array;
+  HEAP8: Int8Array;
+  HEAP16: Int16Array;
+  HEAP32: Int32Array;
+  HEAPU8: Uint8Array;
+  HEAPU16: Uint16Array;
+  HEAPU32: Uint32Array;
+  HEAPF32: Float32Array;
+  HEAPF64: Float64Array;
+  TOTAL_STACK: number;
+  TOTAL_MEMORY: number;
+  FAST_MEMORY: number;
+  _malloc(size: number): number;
+  _free(ptr: number): void;
+
+  FS: FS;
+
+  CommQueryExecutor: CommQueryExecutorType;
+}