Execution Context & Resolver

public interface MongoTemplateResolver<K> {
  MongoExecutionContext getTemplate(K key);
}

MongoClient frontClient = MongoClients.create(frontConnectionString);
MongoClient backClient = MongoClients.create(backConnectionString);

MongoExecutionContext frontContext = new DriverMongoExecutionContext(
    frontClient,
    frontClient.getDatabase("front")
);

MongoExecutionContext backContext = new DriverMongoExecutionContext(
    backClient,
    backClient.getDatabase("back")
);

MongoTemplateResolver<MongoTemplateName> resolver = key ->
    key == MongoTemplateName.BACK ? backContext : frontContext;

MongoExecutionContext context = new DriverMongoExecutionContext(
    mongoClient,
    mongoDatabase,
    entityClass -> collectionNameResolver(entityClass)
);