Engineering Cheat Sheets
Distilled, verified reference sheets covering System Design latency numbers, Spring Boot 3 annotations, DSA Big-O complexities, and production incident triage.
Latency Numbers Every Systems Architect Must Know
Humanized physical latency limits and order-of-magnitude hardware invariants essential for back-of-the-envelope capacity estimations in system design interviews.
CPU on-chip cache. Extremely fast register-level memory access.
~14x slower than L1 cache. Shared across immediate CPU cores.
~200x slower than L1. Foundation for in-memory stores like Redis and Memcached.
~100x slower than RAM. Modern solid-state storage boundary.
Spring Boot 3 & Spring 6 Annotations Master Matrix
Comprehensive reference guide to core IoC stereotypes, AOP boundaries, configuration binding, and modern declarative client annotations in Spring Boot 3.5.
Combines @Configuration, @EnableAutoConfiguration, and root package @ComponentScan.
@Repository additionally translates vendor-specific SQL exceptions to Spring DataAccessException.
Wraps method in dynamic proxy. Bypassed by self-invocation (this.method()).
Instructs container which specific bean candidate to inject when multiple match the interface.
Data Structures & Algorithms Big-O Complexity Chart
Time and space complexity cheat sheet covering fundamental data structures, search algorithms, and graph traversal invariants.
Contiguous memory ensures direct address calculation. Resizing costs amortized O(1).
Non-contiguous heap pointers. Insert/delete at known pointer is O(1).
Worst case O(n) occurs under hash collision clustering (Java 8 treeifies buckets to O(log n)).
AVL and Red-Black tree rebalancing guarantees O(log n) height invariant.
SQL Transactions, ACID & Concurrency Anomalies
Matrix of ANSI SQL transaction isolation levels, read phenomena, and Multi-Version Concurrency Control (MVCC) locking trade-offs.
Transactions read uncommitted changes made by other transactions. Rarely used in production.
Default in PostgreSQL, Oracle, and SQL Server. Only committed data is read; repeatable reads not guaranteed.
Default in MySQL InnoDB. Snapshot isolation prevents non-repeatable reads; InnoDB MVCC also prevents phantoms.
Strict serializable execution. Implemented via SSI (Postgres) or two-phase locking (2PL).
Linux Production Incident Triage & SRE Cheatsheet
High-velocity command line recipes for diagnosing CPU saturation, memory exhaustion, network packet drops, and disk I/O bottlenecks during live outages.
Inspect 1, 5, 15 minute load averages against total CPU core count (nproc).
Check available memory and si/so columns for active kernel swap thrashing.
Inspect %util and await columns. %util > 90% indicates disk bottleneck.
Display active listening sockets, process IDs, and backlog queue sizes.