Handling Concurrency and Race Conditions
Modern applications serve many users at once. Occasionally two actions collide — two people buy the last item in stock at the same instant. Without care, this creates a race condition and inconsistent data.
Handling concurrency correctly ensures your system behaves sensibly under load, which becomes more important the more successful your product is.
What Can Go Wrong
If two requests read the same value, both decide they can proceed, and both write back, one update can quietly overwrite the other. The result is oversold stock, duplicate bookings or lost edits.
How We Prevent It
- Locking a record briefly so only one update wins.
- Checking a value has not changed before saving.
- Using the database's own atomic operations where possible.
Why It Matters as You Scale
These issues are rare at low traffic and common at high traffic. Designing for concurrency early means growth brings revenue, not chaos.
Testing the Tricky Cases
Race conditions are notoriously hard to spot because they depend on precise timing. We deliberately test the awkward scenarios — simultaneous purchases, rapid repeat clicks, parallel updates — so that the safe behaviour is proven rather than assumed. It is far cheaper to catch these in testing than to refund an oversold order later.
If you need a hand with any of this, your Progressive Robot delivery team is ready to help. Raise a ticket from the Support area of your client portal or speak to your account manager and we will guide you through the next steps.