MJVM2LL/A is this a good little computer

Those part numbers are location-specific and can vary according to your location on Earth,

Rather than use that number, identify that MacBook model by following these instructions: Identify your MacBook model - Apple Support.

If the Mac is not yet yours, ask the prospective seller to follow them and let you know exactly which model it is. The Model Identifier is ideally what you want to know.

That MJVM2LL/A model is a bottom-end US model MacBook Air 11” model with 128 GB storage from 2015.

Unknown which of the available Intel processors, and unknown how much memory.

It’s too old for current macOS. macOS Monterey is the end of the line, and it won’t run (current) macOS Ventura.

128 GB storage isn’t all that useful; it’ll be tight for even light usage.

It’ll very likely be inadequate for heavier use, or for tasks such as app development. Particularly if it’s the 8 GB memory model. But it’s old and slow and storage-limited.

It’s also the previous processor architecture; Intel. Apple has moved on to Apple silicon AArch64 Arm processors in recent years.

Make sure the Mac is not Activation Locked.

Whether this Mac works for your needs and budget?

If what MrHoffman wrote is correct — and I have no doubt that it is — and if you are thinking of purchasing that Mac, don't. It was intended to be an entry-level device suitable for little more than email and websites that are not particularly demanding.

Even if it were not so modestly configured, at nearly eight years old, it is near if not already past any reasonable expectation of a useful life.