message: Fixed issue with memoizing IModelDb.open() calls.
diff: @@ -11,6 +11,9 @@ const loggingCategory = "imodeljs-backend.OpenIModelDb";
  * @hidden
  */
  export class OpenIModelDbMemoizer extends PromiseMemoizer<IModelDb> {
  +
  + private static _openIModelDbMemoizer: OpenIModelDbMemoizer;
  +
  public constructor() {
  super(IModelDb.open, (accessToken: AccessToken, contextId: string, iModelId: string, openParams: OpenParams, version: IModelVersion): string => {
  return `${accessToken.toTokenString()}:${contextId}:${iModelId}:${JSON.stringify(openParams)}:${JSON.stringify(version)}`;
  @@ -33,7 +36,9 @@ export class OpenIModelDbMemoizer extends PromiseMemoizer<IModelDb> {
  Logger.logTrace(loggingCategory, "Received OpenIModelDbMemoizer.openIModelDb request at the backend", () => (iModelToken));
  - const { memoize: memoizeOpenIModelDb, deleteMemoized: deleteMemoizedOpenIModelDb } = new OpenIModelDbMemoizer();
  + if (!OpenIModelDbMemoizer._openIModelDbMemoizer)
  + OpenIModelDbMemoizer._openIModelDbMemoizer = new OpenIModelDbMemoizer();
  + const { memoize: memoizeOpenIModelDb, deleteMemoized: deleteMemoizedOpenIModelDb } = OpenIModelDbMemoizer._openIModelDbMemoizer;
  const qp = memoizeOpenIModelDb(accessTokenObj!, iModelToken.contextId!, iModelToken.iModelId!, openParams, iModelVersion);
  