This article explains how MySQL handles auto‑increment primary keys, InnoDB internal row_id, Xid, trx_id, and thread_id when their numeric limits are reached, illustrating the resulting errors, data overwrites, and potential consistency bugs with practical SQL examples and verification steps.
A backend engineer discovers that a massive MySQL table’s auto‑increment INT primary key reached its maximum value, causing insert failures, and walks through detailed analysis, three remediation options—including switching to BIGINT, redesigning IDs, and sharding—plus practical scripts, performance measurements, and lessons learned about concurrency and schema design.
This article analyzes the interview focus on MySQL auto‑increment primary key exhaustion, explains the underlying mechanism, outlines preventive design choices and monitoring, and provides detailed emergency response options, best‑practice recommendations, and common pitfalls for robust database management.
When a MySQL table's auto‑increment primary key approaches its maximum value, you can avoid failures by converting the column to BIGINT, switching to UUIDs, using segmented ID generators, composite keys, adjusting the increment step, or applying database sharding.
The article recounts a MySQL production incident where an INT auto‑increment column reached its maximum value, causing insert failures, and walks through analysis, three remediation options, a stored‑procedure cleanup, a conversion to BIGINT, performance monitoring, and lessons on concurrency and schema design.
This article compares three common distributed ID generation methods—database auto‑increment, UUID, and Snowflake—detailing their architectures, advantages, drawbacks, and ideal use‑cases to help engineers select the most suitable approach for their systems.
This guide compares four common distributed ID generation techniques—database auto‑increment, UUID, Twitter’s Snowflake, and Redis INCR—detailing their advantages, drawbacks, and ideal use‑cases, helping architects select the most suitable method for their system’s scalability and performance requirements.
This article experimentally compares auto‑increment, UUID and Snowflake‑generated primary keys in MySQL, analyzes their index structures, shows insertion‑time benchmarks, discusses the trade‑offs of each approach, and concludes that sequential auto‑increment keys deliver the best overall performance.
A massive MySQL table with billions of rows ran out of INT auto‑increment IDs, causing insert failures; the article walks through the root cause analysis, three migration strategies, practical BIGINT conversion steps, performance monitoring tricks, and lessons learned about schema design and concurrency.
A massive MySQL table ran out of INT auto‑increment IDs due to high concurrency, leading to insert failures; the article analyzes the root cause, evaluates three remediation strategies, and details the eventual migration to BIGINT with performance monitoring and code snippets.
This article explores how to replace long UUIDs with short, sequential numeric IDs by evaluating Snowflake, MySQL auto‑increment tables, REPLACE INTO deadlock issues, batch allocation strategies, and a final free‑ID table design that balances performance, simplicity, and low ID waste.
The article recounts a real‑world incident where a massive MySQL table exceeded the INT auto‑increment limit, causing insert failures, and walks through analysis, three remediation strategies—including converting to BIGINT, using distributed IDs, and sharding—plus practical SQL scripts and performance insights for handling billions of rows.
This article examines how auto‑increment primary keys work, the limits of common integer types, the failures that occur when those limits are reached, and practical strategies—including type upgrades, distributed ID generators, sharding, and sequence cycling—to prevent and mitigate ID exhaustion in high‑traffic MySQL and PostgreSQL deployments.
This article explores how to replace long Snowflake IDs with concise numeric account IDs by leveraging MySQL auto‑increment tables, addressing deadlock pitfalls of REPLACE INTO, and evaluating alternative batch‑allocation and sharding strategies before presenting a final free‑ID table design.
This article recounts a real‑world MySQL incident where the auto‑increment INT overflowed after billions of rows, explores why the ID limit was reached, evaluates three remediation strategies—including switching to BIGINT, distributed IDs, and sharding—and shares practical SQL scripts and performance insights.
A massive MySQL table reached the INT auto‑increment ceiling, causing insert failures; the article details how the issue was identified, explores three remediation strategies—including converting the column to BIGINT, redesigning IDs, and sharding—shows stored‑procedure scripts, performance monitoring, and practical lessons on schema design and multithreaded batch processing.
A senior architect investigates a missing device error caused by MySQL auto‑increment IDs reaching the 32‑bit integer limit, analyzes the overflow issue, evaluates three remediation strategies—including converting the column to BIGINT, adopting distributed IDs, or sharding the database—and shares practical code snippets and performance insights for large‑scale data migrations.
An in‑depth MySQL study compares auto‑increment, UUID, and random Snowflake keys by building three identical tables, running insert‑performance tests with Spring Boot/JdbcTemplate, and analyzing index structures, revealing why auto‑increment keys outperform UUIDs despite the latter’s uniqueness.
MySQL auto‑increment primary keys are expected to be sequential, but deletions, manual IDs, transaction rollbacks, unique‑key conflicts, and bulk‑insert allocation strategies can all cause gaps, and this article explains each scenario in detail.
To replace long UUIDs with short, sequential numeric account IDs, the article explores the limitations of Snowflake’s 64‑bit IDs, evaluates MySQL auto‑increment and REPLACE INTO approaches, identifies deadlock issues, and ultimately proposes a segmented free‑ID table with batch allocation to achieve compact, ordered IDs.
The article examines the challenges of generating short, user‑friendly numeric account IDs, evaluates Snowflake and MySQL auto‑increment approaches, discusses deadlock issues with REPLACE INTO, and presents a final segment‑based solution that allocates ID blocks per login server while avoiding waste and concurrency problems.
When MySQL auto‑increment IDs approach their limit, this guide explains six practical solutions—including expanding column types, using UUIDs, segmenting ID generation, composite keys, adjusting increment steps, and sharding databases—to ensure scalable, unique identifiers for large‑scale applications.
This article explores the evolution from using the Snowflake algorithm to a MySQL‑based short numeric ID generation scheme, detailing challenges such as long IDs, deadlocks with REPLACE INTO, and presenting a segment‑based solution that allocates ID blocks, tracks unused IDs, and avoids concurrency issues.
This article discusses the problem of MySQL auto‑increment ID exhaustion and presents six practical solutions—including changing column type to BIGINT, using UUIDs, segmenting ID generation, composite keys, adjusting auto‑increment steps, and database sharding—to ensure scalability and uniqueness.
This article investigates MySQL's recommendation to avoid UUIDs and non‑sequential keys by benchmarking insert performance of auto‑increment, UUID, and random (snowflake) primary keys, analyzing their index structures, drawbacks, and concluding that sequential auto‑increment keys provide the best overall efficiency.
This article investigates MySQL’s recommendation against UUIDs, comparing auto‑increment, UUID, and random snowflake keys through insertion speed tests and index structure analysis, revealing why auto‑increment keys outperform others, while also discussing the drawbacks of each approach.
This article investigates MySQL's recommendation against using UUIDs or non‑sequential keys as primary keys by creating three tables, benchmarking insert and query speeds with Spring Boot/JdbcTemplate, analyzing index structures, and discussing the trade‑offs of auto‑increment, UUID, and random long keys.
This article investigates MySQL's recommendation against using UUID or random Snowflake IDs as primary keys by creating three tables with different key strategies, running Spring Boot/JDBC performance tests, analyzing index structures, and concluding that auto‑increment keys offer superior insertion efficiency and fewer drawbacks.
This article experimentally compares MySQL auto_increment, UUID, and random Snowflake keys by measuring insert and query speeds, analyzing InnoDB index behavior, and discussing the trade‑offs of each primary‑key strategy, ultimately showing why auto_increment generally outperforms UUID in large‑scale workloads.
Benchmarking three MySQL tables—auto_increment, UUID, and random long keys—shows that sequential auto_increment inserts are fastest, random keys are slower, and UUIDs dramatically lag due to random I/O and fragmentation, so use auto_increment for most workloads and reserve UUIDs only for required global uniqueness.
This article analyzes why MySQL 8.0.13 introduced the sql_require_primary_key parameter, demonstrates how adding auto‑increment primary keys can cause master‑slave data inconsistencies, explains the underlying InnoDB row‑id behavior, and provides a step‑by‑step solution to synchronize tables.
This article examines MySQL's recommendation against UUID primary keys by creating three tables with different key strategies, running large‑scale insert tests using Spring JdbcTemplate, and analyzing the resulting performance, index behavior, and trade‑offs of auto‑increment, UUID, and random keys.
MySQL 8 removes the VALUES(col) function, requiring developers to use an alias with INSERT INTO ... VALUES (...) AS alias and to reference columns via alias.col in ON DUPLICATE KEY UPDATE, while also changing AUTO_INCREMENT and auto‑update column behaviors.
This article explains why MySQL auto‑increment IDs can run out in large or special‑case tables and presents six practical solutions—including changing the column type to BIGINT, using UUIDs, segmenting IDs, composite keys, adjusting auto‑increment steps, and sharding databases—to ensure scalable and unique primary keys.
This article explains the mechanisms behind MySQL auto‑increment primary keys, why gaps appear after failed inserts, unique‑index violations, transaction rollbacks, and batch operations, and how storage engines and innodb_autoinc_lock_mode settings influence the continuity of generated IDs.
This article explains why MySQL auto‑increment primary keys can become non‑continuous, covering storage mechanisms, unique‑index violations, transaction rollbacks, batch inserts, and step‑size settings, and provides practical examples and diagrams to help developers diagnose and avoid ID gaps.
This article investigates MySQL's recommendation against using UUID or non‑sequential random IDs as primary keys by benchmarking auto‑increment, UUID, and Snowflake‑derived keys, analyzing their insertion speed, index behavior, and discussing the advantages and drawbacks of each approach.
While MySQL INT and BIGINT auto‑increment columns usually suffice, this article explains their numeric limits, calculates how many records each can store over time (e.g., at 100 inserts per second), and provides practical steps to switch from INT to BIGINT safely.
This article analyzes MySQL's recommendation to avoid UUID or non‑sequential random primary keys by benchmarking insert performance across three tables—auto_increment, UUID, and random key—explaining the underlying index structures, observed speed differences, and the trade‑offs of each approach.
This article explains the architecture of MySQL's InnoDB storage engine locks, covering server‑level metadata locks, table‑level shared and exclusive locks, intent locks, and the three modes of AUTO‑INC locks, with practical SQL examples and performance‑schema queries.
This article analyzes why MySQL recommends auto‑increment primary keys over UUIDs or random snowflake IDs by designing three tables, running insert‑select benchmarks with Spring Boot's JdbcTemplate, presenting the test results, and discussing the underlying index‑structure impacts and trade‑offs.
In MySQL 5.7, using REPLACE INTO on a table that has an auto‑increment primary key and an extra unique index can cause the master and slave AUTO_INCREMENT counters to diverge, leading to duplicate‑key errors after failover, a bug mitigated by upgrading to MySQL 8.0, manual counter fixes, or avoiding REPLACE INTO.
This article explains how MySQL auto‑increment primary keys work, the practical limits of various internal IDs such as auto‑increment, InnoDB row_id, Xid, trx_id, and thread_id, and compares them with external solutions like Redis‑based auto‑increment keys, providing guidance on choosing the right approach for different scenarios.
Understanding MySQL’s auto‑increment mechanism reveals why IDs can become non‑sequential due to storage differences, transaction rollbacks, unique key conflicts, and batch inserts, and shows how lock‑mode settings and MySQL 8.0 improvements can optimize performance and maintain consistency.
This article explains why MySQL uses locks, categorizes lock types from global to row level, details their implementation and commands, and shows how intention, metadata, and auto‑increment locks work while offering strategies to prevent deadlocks and lock contention.
This article examines MySQL's comprehensive lock taxonomy, starting from common row and table locks, then delving into lesser‑known mechanisms such as global locks, intention locks, auto‑increment locks, and Latch, while explaining their commands, use‑cases, and performance implications for developers and DBAs.
This article compares UUID and auto‑increment primary keys in MySQL, explaining how each is generated, their advantages and drawbacks, performance implications, and practical guidance on selecting the right key type for different business scenarios.
This article explains how MySQL handles overflow of auto_increment, InnoDB row_id, Xid, trx_id, and thread_id, showing the resulting primary‑key errors, data overwrites, rare Xid collisions, a potential dirty‑read bug, and recommended safeguards such as using BIGINT.
This article analyzes MySQL's recommendation against UUIDs and non‑sequential keys by benchmarking three tables—auto‑increment, UUID, and random snowflake IDs—using a Spring Boot JdbcTemplate test, revealing that sequential primary keys provide superior insert performance and lower index fragmentation.
This article analyzes why MySQL recommends auto_increment primary keys over UUID or non‑sequential Snowflake IDs by creating three tables, running Spring Boot/JdbcTemplate performance tests, and examining index structures, lock contention, and fragmentation to guide optimal primary‑key selection.
This article explains how MySQL stores and updates auto‑increment values, why gaps appear after failed inserts, unique‑key conflicts, transaction rollbacks or batch operations, and how different innodb_autoinc_lock_mode settings and MySQL 8.0 improvements can mitigate the issue.
This article explains why AUTO_INCREMENT is unsupported in OceanBase Oracle tenants, introduces four practical ways to implement auto‑increment columns using sequences, DML, DDL, triggers, and the GENERATED BY DEFAULT AS IDENTITY syntax, and provides step‑by‑step SQL examples for each method.
The article explains how MySQL auto‑increment primary keys, InnoDB invisible row_id, transaction Xid and trx_id, and thread identifiers behave when they reach their numeric limits, showing the resulting errors, data overwrites, and potential visibility bugs in long‑running instances.
This article explains how MySQL handles auto‑increment primary keys, InnoDB’s internal row_id, transaction Xid and trx_id counters when they reach their maximum values, the resulting primary‑key conflicts, data overwrites, and a theoretical dirty‑read bug caused by counter wrap‑around.
This article explains the different types of auto‑increment identifiers used by MySQL—including table primary keys, InnoDB row_id, Xid, trx_id, and thread_id—covers their limits and behaviors when they overflow, and introduces Redis as an external auto‑increment key solution.
This article investigates MySQL's recommendation against using UUIDs as primary keys by creating three tables with auto‑increment, UUID, and random (snowflake) keys, running insertion benchmarks with Spring Boot/JdbcTemplate, analyzing index structures, and discussing the advantages and drawbacks of each key strategy.
The article presents a detailed performance comparison between auto‑increment integer primary keys and UUID string primary keys in MySQL, including table definitions, 5‑million‑row and 10‑million‑row test results for read, range, write, backup, and storage efficiency, and offers practical recommendations for choosing the appropriate key strategy in distributed environments.
This article explains how MySQL auto‑increment primary keys, InnoDB hidden row_id, transaction Xid, InnoDB trx_id, and the server thread_id behave when they reach their numeric limits, the consequences for data integrity, and recommended mitigation strategies.
This article investigates MySQL's recommendation against using UUIDs as primary keys by creating three tables (auto‑increment, UUID, and random snowflake IDs), benchmarking insert speeds with Spring Boot/JdbcTemplate, analyzing index structures, and discussing the advantages and drawbacks of each key strategy.
This article explains how MySQL's auto‑increment primary keys behave when they reach their maximum value, the internal InnoDB row_id mechanism, the generation of Xid and trx_id for transactions, and the handling of thread identifiers, including practical examples and code snippets.
This article explains how MySQL’s various auto‑increment identifiers—table AUTO_INCREMENT, InnoDB row_id, Xid, trx_id, and thread_id—behave when they reach their maximum values, the resulting errors or data overwrites, and the underlying mechanisms that cause these edge‑case behaviors.
This article examines MySQL's recommendation to use auto_increment primary keys instead of UUIDs or random keys by creating three comparable tables, inserting large data sets with Spring JdbcTemplate, and analyzing insertion speed, index structure impact, and the trade‑offs of each key strategy.
This article explains the concept of MySQL auto‑increment locks, describes different insertion methods and lock modes, analyzes how InnoDB allocates and manages auto‑increment IDs—including simple, bulk, and mixed inserts—and provides source‑code insights, practical experiments, and mitigation strategies for ID continuity issues.
This article investigates MySQL's recommendation against UUID primary keys by creating three tables—auto‑increment, UUID, and random (snowflake) keys—running insert and query benchmarks with SpringBoot/JdbcTemplate, analyzing index structures, and discussing the performance trade‑offs and security considerations of each key strategy.
This article investigates MySQL's recommendation to use auto_increment primary keys instead of UUID or random snowflake IDs by comparing table designs, running SpringBoot‑based insert benchmarks, analyzing index structures, and discussing the performance trade‑offs and practical drawbacks of each approach.
This article investigates MySQL's recommendation to avoid UUIDs as primary keys by benchmarking auto‑increment, UUID, and random snowflake IDs using Spring Boot and JdbcTemplate, analyzing insert speed, InnoDB index behavior, and the trade‑offs of each key strategy.
This article explains how MySQL allocates auto‑increment IDs, the differences between MySQL versions, the three InnoDB lock modes, scenarios that break ID continuity, what to do when IDs run out, and strategies to hide sequential IDs from malicious crawlers.
This article evaluates MySQL insertion performance of three primary key strategies—auto‑increment, UUID, and random Snowflake‑like keys—by building identical tables, running Spring‑Boot/JdbcTemplate benchmarks, analyzing index structures, and discussing the advantages and drawbacks of each approach.
This article explains the different types of auto‑increment identifiers used by MySQL—including table primary keys, InnoDB row_id, Xid, trx_id, and thread_id—describes how they reach their maximum values, the consequences of overflow, and compares external solutions such as Redis‑based keys.
The article examines the 2012 GitHub data‑leak caused by MySQL master‑slave failover and auto_increment misuse, explains why developers' expectations of uniqueness, monotonicity and continuity are unrealistic, and proposes half‑sync replication and distributed ID algorithms like Snowflake as more reliable solutions.
This article explains the various types of auto‑increment identifiers in MySQL—including table primary keys, InnoDB row_id, Xid, trx_id, thread_id—and discusses their maximum values, overflow behavior, and alternative solutions such as using Redis for external unique keys.
This article explains why MySQL's auto‑increment counter can be lost after a server restart for InnoDB tables, compares the behavior with MyISAM, demonstrates the problem with practical SQL examples, and shows how MySQL 8.0 fixes the counter logic.
A developer encountered a duplicate‑key error caused by an unexpected primary‑key update that overflowed the signed INT limit, exposing a hidden MySQL auto‑increment bug that persisted across normal inserts until a later DDL operation triggered failures, a problem present in Percona 5.6/5.7 but fixed in MySQL 8.0.
This article explains the concept of locks in computing and databases, compares InnoDB and MyISAM storage engines, details transaction isolation phenomena such as dirty reads, non‑repeatable reads and phantom reads, and explores InnoDB lock types, lock algorithms, intention locks, auto‑increment lock modes, and MVCC mechanisms.
This article explains MySQL AUTO_INCREMENT behavior, demonstrates creating tables with unsigned int primary keys, shows how to set and inspect the AUTO_INCREMENT value, discusses its maximum limits, and recommends using bigint or explicit primary keys to avoid overflow and duplicate‑key errors.
This article investigates why MySQL recommends auto_increment over UUID or non‑sequential snowflake IDs by creating three tables, running insert and query benchmarks with Spring Boot and JdbcTemplate, analyzing index structures, and summarizing the performance trade‑offs and security considerations of each primary‑key strategy.
This article explains how MySQL integer auto‑increment primary keys can reach their maximum value, the resulting duplicate‑key errors, and how using BIGINT or understanding InnoDB's internal row_id behavior can prevent data loss or crashes.
This article explains how MySQL InnoDB generates AUTO_INCREMENT values, compares the full‑table locking mechanism before version 5.1 with the lightweight mutex introduced in 5.1, and describes the further improvements in 8.0 that rely on row‑based replication and lock‑mode settings.
The article explains the concept and requirements of primary keys in MySQL, outlines best practices such as avoiding updates and reuse, and discusses how primary keys serve as clustered indexes in InnoDB, highlighting the performance advantages of using business‑agnostic auto‑increment IDs over random keys.
This article examines MySQL's recommendation to use auto_increment primary keys instead of UUID or random snowflake IDs by creating three tables, running insertion benchmarks with Spring Boot and JdbcTemplate, and analyzing how index structure affects performance and scalability.
This article explains MySQL primary key design principles, compares auto‑increment, UUID and uuid_short approaches, provides SQL examples and performance benchmarks, and offers guidance on choosing business‑related versus unrelated key columns for optimal data integrity and query efficiency.
After upgrading a critical MySQL 5.6 table to 5.7, the system began reporting duplicate‑key errors on master, replica and read‑only instances due to unexpected changes in the AUTO_INCREMENT value, prompting a deep kernel investigation, bug analysis, on‑site reproduction, and practical mitigation steps.
This article introduces the concept of distributed IDs, outlines the required properties of global uniqueness, high availability, performance and simplicity, and compares six generation schemes—UUID/GUID, database auto‑increment, random numbers, random strings, Snowflake, and MongoDB ObjectID—detailing their structures, advantages and disadvantages.
This article examines common MySQL pitfalls—including signed vs. unsigned integers, auto‑increment key requirements, varchar length versus byte count, case‑insensitive collations, and storing emoji characters—providing concrete SQL examples, error screenshots, and configuration tips to help developers avoid unexpected errors.
This article creates three MySQL tables with auto‑increment, UUID, and Snowflake‑generated random keys, runs identical insert workloads using Spring Boot and JdbcTemplate, measures performance, compares index structures, discusses the pros and cons of each key type, and concludes with best‑practice recommendations.
This article examines MySQL's recommendation to use auto_increment primary keys instead of UUID or Snowflake IDs by creating three tables, running insertion benchmarks with Spring Boot, comparing index structures, and discussing the performance trade‑offs and practical drawbacks of each approach.
This article investigates why MySQL recommends auto_increment primary keys over UUID or snowflake IDs by creating three tables with different key strategies, running insertion benchmarks using Spring Boot, and analyzing index structures, performance results, and the trade‑offs of each approach.
After upgrading a MySQL 5.6 master to 5.7, inserts on several InnoDB tables began failing with duplicate‑key errors because the auto_increment value became inconsistent, and the article walks through kernel‑level investigation, reproduction steps, bug analysis, and practical fixes.
This article explains PostgreSQL's auto‑increment mechanism, covering built‑in serial data types, manual sequence creation, default value assignment, step‑by‑step code examples, and how to query indexes, offering a clear comparison with MySQL's auto_increment feature.
After upgrading a critical MySQL client from 5.6 to 5.7, duplicate‑key errors appeared during inserts on master, replica and read‑only instances, prompting a deep dive into InnoDB auto‑increment mechanics, related kernel bugs, on‑site analysis, and both application‑side and engine‑side remediation strategies.
After upgrading a critical MySQL 5.6 database to 5.7, inserts on the master began failing with duplicate‑key errors due to unexpected auto‑increment values, prompting a deep dive into InnoDB internals, related bugs, and practical mitigation steps.
This article examines why MySQL auto‑increment primary keys can jump unexpectedly when using REPLACE INTO or INSERT … ON DUPLICATE KEY UPDATE, explains the role of innodb_autoinc_lock_mode, demonstrates examples, and offers practical solutions to prevent uncontrolled ID growth.
The article explains why MySQL's AUTO_INCREMENT primary keys can become non‑monotonic and non‑continuous due to early‑version in‑memory counters, restart behavior, concurrency lock modes, and how MySQL 8.0 persists the counter to mitigate these issues while discussing design trade‑offs and best practices.
This article examines MySQL column attributes—especially NULL vs NOT NULL handling, the impact of NULL on concatenation, COUNT and indexing, as well as AUTO_INCREMENT behaviors, lock modes, step/offset settings, and overflow scenarios—to help developers write more efficient and reliable SQL.
This article explains how InnoDB auto‑increment values behave when the highest ID is deleted, after a MySQL restart, and when IDs are manually set, including experiments and guidance on handling overflow.
This article explains why MySQL auto‑increment primary keys can reach their limit, shows how switching from INT to BIGINT prevents overflow, and reviews three online schema‑change methods—including native ALTER, pt‑osc, and gh‑ost—plus considerations for triggers, foreign keys, and master‑slave setups.
The article analyzes why MySQL tables upgraded from 5.6 to 5.7 began generating duplicate‑key errors during inserts, examines related InnoDB auto‑increment mechanisms, reproduces the issue, discusses known bugs (including replace‑into replication problems), and proposes both operational and kernel‑level solutions.
This article presents nine classic MySQL error cases—from connection limits and replication conflicts to installation permission issues, forgotten passwords, auto‑increment resets, character‑set garbling, binlog misconfiguration, timeout problems, and file‑open limits—each accompanied by clear diagnosis steps and practical solutions.
The article explains how exposing auto‑increment primary keys can leak business information, illustrates the danger with historical examples, and evaluates alternative ID generation strategies such as encoding, UUIDs, and Snowflake‑style distributed IDs, including performance comparisons in MySQL.
The article explains how InnoDB’s auto‑increment handling changed after MySQL 5.1.22—from using a table lock to a lightweight mutex for predictable‑row inserts—and details the three innodb_autoinc_lock_mode settings, their impact on concurrency and replication, and related pitfalls such as non‑sequential IDs.
