I want to use some source code under CC-BY-SA for my company's project. That project is commercial and closed source code. I want our project not to have obligation to release the source code. Is this possible?
You can include CC-BY-SA source code in proprietary software iff you do not publish that software. The CC-BY-SA requirements only apply once you Share the adapted work. For example, this would allow internal tools, or possibly a server backend where that usage does not constitute a public performance.
 as defined in section 1.k in the CC-BY-SA 4.0, compare Distribute and Publicly Perform in sections 1.d and 1.j in the CC-BY-SA 3.0
If you desire to publish software that was adapted from CC-BY-SA source code, you can only do so under the terms of that license. In particular:
- you must publish your software under that version of the CC-BY-SA or a compatible license,
- you must provide proper attribution for the original source code,
- you must not apply additional terms or restrictions, and
- you must not apply technical restrictions such as DRM.
Note that these requirements may be at odds with the terms and conditions of some app stores.
Absent from the CC-BY-SA is the requirement to publish your source code. You can publish CC-BY-SA software in any format you like, including in compiled form. However, recipients of that software are free to reverse-engineer and decompile it, and to adapt that software. So while the CC-BY-SA is generally similar to the GPL, the CC-BY-SA does not require you to publish your preferred form of making modifications (the source code).
Note that most code on Stack Overflow is licensed under the CC-BY-SA 3.0. This means that such code cannot be copied freely, not even for open-source projects, unless they are licensed under a CC-BY-SA 3.0 compatible license (which, indirectly, includes the GPLv3).