Best services for client data upload, data cleaning, ingestion into RDS

Is this CSV a custom one or some database backup etc. ? Assuming that its former, then is R a mandate requirement to use? One quick option would be to use AWS Glue which can be used to do your ETL. The source of CSV can be S3. Glue automatically generates Scala or Python code for your ETL jobs that you can further customize using tools you are already familiar with.