The Scrum guide by scrum.org doesn’t mention spikes, but it has something else: the Product Backlog Refinement. And this often gets mistaken for a Scrum Event that puts the entire Development Team in a room with the Product Owner for half a day a week. The entire team then looks at the top of the product backlog and tries to uncover all the details there. They do this until enough uncertainties are uncovered and the team feels confident it can estimate. It gets worse when there is a project manager on board who needs estimations to discuss budgets and delivery dates before deciding whether he wants a story at all. This way, you end up spending a lot of time on value you’re not delivering. At some point, somebody will say: This is taking too long; let’s make it a spike and move on. And that’s not what spikes are for.
A spike is a concept from Extreme Programming (XP) where the team does a technical examination of possible solutions before committing to one to solve a requirement. Like many concepts from XP (for example: Daily Standup vs Daily Scrum), it’s found its way into many Scrum projects. The Scrum Alliance adopts and expands the concept by saying it is a story-like backlog item that yields information rather than a working increment of software. This information can be both technical or functional and is deemed necessary before deciding on whether or not to implement a functional story. And if so, it ensures that enough information is available to know how. The Scrum Alliance warns that a spike should be used sparingly, if at all.