Here’s the difference between Singer and Skyvia. The comparison is based on pricing, deployment, business model, and other important factors.
Singer is an open-source standard for writing scripts that move data between databases, web APIs, files, queues, and just about anything else you can think of
Skyvia is a cloud service for data integration and backup. It allows users to integrate data in their cloud applications and relational databases, as well as perform data backup and restore operations. Skyvia supports a wide range of database servers (SQL Server, MySQL, PostgreSQL etc.), popular CRM systems (Salesforce, Dynamics CRM, Zoho CRM, SugarCRM), and other data sources (Dropbox, FTP, Box, Google Drive etc). Skyvia is free for now but has a plan to monetize the product.