FFmpeg customization

I am looking for a freelancer who can help me customize FFmpeg for my project that uses ffmpeg to transcode *.mp4 files into different resolutions whenever a user uploads a video. But once the transcoding is completed it automatically delete the input (original) file. I want to keep the original file. I need someone who can customize the ffmpeg code so that after transcoding it keeps the original file.

Ideal skills and experience:
- Expertise in FFmpeg customization and configuration
- Familiarity with Linux operating systems
- Strong understanding of video encoding and decoding technologies