What is checkpoint?

A checkpoint is a saved snapshot of a system’s current state at a specific moment. It records enough information (like memory contents, program counters, open files, etc.) so that the system can later be restored to that exact point, as if time were turned back.

Let's break it down

  • State: All the data that defines what a program or system is doing right now.
  • Snapshot: A copy of that state taken at a particular instant.
  • Save: The snapshot is written to a storage medium (disk, SSD, cloud).
  • Restore: Later, the saved snapshot can be loaded to bring the system back to the saved point, discarding any work done after the checkpoint.

Why does it matter?

Checkpoints let you recover from failures without starting over, save progress during long tasks, and enable features like “undo,” migration, and load balancing. They reduce downtime and wasted work, which is especially important for big data jobs, scientific simulations, and critical services.

Where is it used?

  • Operating systems: Hibernation or crash recovery.
  • Databases: Transaction logs and backup points.
  • High‑performance computing: Long scientific simulations that run for days.
  • Machine learning: Saving model weights during training so you can resume later.
  • Virtual machines & containers: Snapshots for quick rollbacks or migrations.

Good things about it

  • Fault tolerance: Quickly bounce back after crashes or power loss.
  • Time savings: No need to redo work that was already completed.
  • Flexibility: Enables migration, scaling, and testing different scenarios from the same starting point.
  • Safety net: Provides a reliable “undo” point for critical operations.

Not-so-good things

  • Performance overhead: Creating and storing checkpoints can slow down the running process.
  • Storage cost: Snapshots take up space, especially for large memory or data sets.
  • Complexity: Implementing correct checkpoint/recovery logic can be tricky, especially in distributed systems.
  • Staleness risk: If checkpoints are taken infrequently, a failure may still cause loss of recent work.