1. Start with a provocative and almost hyperbolic (true) statement, and then don't answer it... leave the viewer hanging. Example: "Everyone knows Lambda is a black box and impossible to debug. No inspector API! Everyone is wrong. WE can make Lambda dance. Watch this magic." --> This crappy intro which I pulled out of thin air sets a particular tone: very casual, a little cocky. That might or might not be the way you want to brand your product. But the point is that it grabs your attention and leaves the viewer saying "Whaaaaa????". And then they keep watching, and the emotional part of the brain is engaged so they're fully engaged.
2. Quick demo. Keep it punchy. For a 30-second demo, this could be all of 10 seconds: click, click, click, and we're done. Skip over anything remotely irrelevant. You can cover that later in a detailed walkthrough.
3. Recap: [Product] does [value] even when [obstacle]. Our [technology] makes it possible to [restate value in different words].
4. Logo.
For a longer demo, you'll want to stretch things out more. Tell a story perhaps, maybe go into more detail. But as always, consider your audience and the emotional beats. You'll want to start with a hook (a provocative unanswered question or declaration), then proceed through the demo which answers the question, then restate what you just said.
A subtle nuance here: never ask the viewer to imagine themselves in a situation, just go with the solution. So not "Have you ever found yourself [problem statement]", but instead start immediately with "[Solution to impossible problem]". If you ask the viewer to imagine themself having a problem, their brain will still be working on the imagining (which is hard work!) and they'll miss the solution. If you jump strait to the solution, anyone who's had that problem will immediately place themself in the situation and go "wait how is that even possible?!?". Don't make someone's brain work harder than it has to.
Lastly: remember that delivery matters. You should be providing energy. If you're talking in a monotone nobody cares. Repetition matters here... if I'm recording a talk I might rehearse it word for word 10-20 times before landing on a delivery that I think is good enough. Keep polishing your word choice, pacing, etc. All those casual, easy voice-overs you've seen are smooth because of practice not because of some un-learnable raw talent.