Realm adding extra size to my apk

You can use abi splits to reduce size of APK.

Normally (without splits) it includes files to support almost all architectures (ARM7, ARMv7, ARM64, x86, MIPS) This is why it's too big.

With abi splits, android studio will generate APK for each architecture, and each APK will not include files for any other architecture

Just add below section in gradle file. Also check this realm documentation

splits {
    abi {
        enable true
        reset()
        include 'armeabi', 'armeabi-v7a', 'arm64-v8a', 'mips', 'x86', 'x86_64'
    }
}

Important

Each distrubtion(APK) will only work on appropriate device. So we can say, app-x86_64-release.apk will not work on armeabi-v7a architectured device. If you try, you'll face Failure [INSTALL_FAILED_NO_MATCHING_ABIS] error.

You can also check these documentations.

• Multiple APK Support
• Configure APK Splits