CRDTs
Data types that converge without coordination, and the semantics you must accept.
5 to work through
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advanced
A collaborative field-notes app uses a CRDT set per project so devices can edit offline and merge without a server decision. Two years in, projects that are heavily edited take 40 seconds to open on a mid-range phone and the local database is 900 MB. Nothing has failed. What is happening, and what would you have designed differently?
3 min answer -
advanced
A collaborative product must let several devices edit the same records, including offline. When are CRDTs the right answer, and when is server authority simpler?
2 min answer -
advanced
A team proposes CRDTs for a collaborative document editor. What do you check before agreeing?
2 min answer -
advanced
An inspection app keeps each site's checklist in an observed-remove set CRDT and synchronises by sending the whole replica state on every reconnect. 6,000 devices on cellular, roughly 40,000 elements per site set, about eight reconnects a day. Roughly how many bytes per device-day, and what does the number rule out?
2 min answer -
advanced
Conflict-free replicated data types guarantee convergence without coordination. What do they cost, and when is the guarantee not enough?
1 min answer
3 terms in this topic
Convergence Without Coordination
The property that replicas applying the same set of updates in any order reach the same state, which is what removes the need for a central arbiter.
conceptCRDT
A data structure whose concurrent updates always merge to the same result regardless of order, removing the need for coordination or conflict resolution.
conceptTombstone Accumulation
The unbounded growth of deletion markers and causal metadata that a coordination-free replica must retain so a peer it has not yet seen cannot resurr…
Neighbouring topics
Edge, Mobile & IoT
General material on architecture beyond the data centre boundary.
Mobile App Architecture
Layering, navigation, background execution, and the platform rules you do not set.
Offline-First
Treating connectivity as an optimisation, with a local store as the source of truth.
Sync & Conflict Resolution
Two devices that both changed the same record while neither could see the other.
Mobile Release Strategy
Store review, staged rollout, and supporting versions you can never force off.
Push & Background Work
Delivery that is best-effort, and an operating system that will kill your process.
Device Identity
Identifying a thing rather than a person, and rotating a credential you cannot type.
Edge Compute Topologies
Regional, metro, on-premises and on-device, and what each tier is genuinely for.
Edge Functions
Short-lived compute at the CDN, its runtime limits, and what must stay at origin.
Edge Data Consistency
Replicated read state at hundreds of locations, and writes that still go to one.
IoT Ingest Architecture
Millions of small, unreliable, frequently duplicated messages arriving continuously.
Device Provisioning
Getting identity and configuration onto hardware at manufacture or first boot.
Fleet Management
Inventory, health, configuration and grouping across devices you will never see.
OTA Updates
Updating firmware over a flaky link, with rollback, and without bricking the device.
Constrained Protocols
MQTT, CoAP and their kin, chosen for power, packet size and intermittent links.
Device Telemetry at Scale
Deciding what a device sends, how often, and what is aggregated before it leaves.
Digital Twin
A server-side model of a physical thing's reported and desired state.
Edge Security & Attestation
Secure boot, hardware roots of trust, and proving what is running on a device.
Physical-World Failure Modes
Power loss, tampering, clock drift, thermal limits, and a truck through the fibre.