MongoSource<String> source = MongoSource.<String>builder()
        .setUri("<mongodb://user:password@127.0.0.1:27017>")
        .setDatabase("my_db")
        .setCollection("my_coll")
        .setProjectedFields("_id", "f0", "f1")
        .setFetchSize(2048)
        .setLimit(10000)
        .setNoCursorTimeout(true)
        .setPartitionStrategy(PartitionStrategy.SAMPLE)
        .setPartitionSize(MemorySize.ofMebiBytes(64))
        .setSamplesPerPartition(10)
        .setDeserializationSchema(new MongoDeserializationSchema<String>() {
            @Override
            public String deserialize(BsonDocument document) {
                return document.toJson();
            }

            @Override
            public TypeInformation<String> getProducedType() {
                return BasicTypeInfo.STRING_TYPE_INFO;
            }
        })
        .build();

Is MongoDB connector doesn't have option to do a filter?