Compare and contrast lock-based, timestamp-based, and optimistic concurrency control mechanisms. Discuss their suitability for different types of transaction processing in distributed databases.

The comparison of Lock-Based, Timestamp-Based, and Optimistic Concurrency Control Mechanisms are as follows:

FeatureLock-Based Concurrency Control (LBCC)Timestamp-Based Concurrency Control (TBCC)Optimistic Concurrency Control (OCC)
ApproachUses locks to control access to resources.Assigns timestamps to transactions and orders them.Allows transactions to run freely and checks for conflicts at commit time.
Conflict HandlingPrevents conflicts by using locks (shared for reads, exclusive for writes).Resolves conflicts based on timestamps (abort & restart if out of order).Detects conflicts at commit time and rolls back conflicting transactions.
Deadlock PossibilityYes, because transactions wait for locked resources.No, transactions do not wait.No, transactions do not block resources.
Abort RateLow, transactions wait instead of aborting.High, transactions often restart if conflicts occur.Moderate to high, depends on the frequency of conflicts.
System OverheadHigh, due to lock management and waiting.Moderate, requires timestamp management but no locks.Low during execution, high at commit time due to validation.
SuitabilityWorks well in high contention environments with frequent updates.Best for read-heavy systems with fewer conflicts.Ideal for low-contention environments with rare conflicts.
Examples of UsageTraditional databases (e.g., MySQL, PostgreSQL with strict locking).Distributed databases (e.g., Spanner, HBase).NoSQL databases, high-performance applications (e.g., Firebase Firestore).

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