Comprehensive Guide to Backend Development: System Design, Architecture, Network Communication, Fault Handling, Monitoring, Service Governance and Deployment

System Development

1. High Cohesion / Low Coupling

High cohesion means a module contains closely related code that performs a single responsibility, while low coupling ensures modules interact through simple interfaces, keeping them independent.

2. Over‑Design

Over‑design adds unnecessary complexity by over‑engineering future requirements, excessive modularisation, and premature use of design patterns.

3. Premature Optimization

Optimising before understanding real performance bottlenecks can make code harder to maintain without delivering benefits; proper testing and profiling should precede optimisation.

4. Refactoring

Refactoring improves code quality and performance by reorganising code without changing its external behaviour, enhancing maintainability and extensibility.

5. Broken‑Window Effect

Just as a broken window invites more damage, allowing code or architectural flaws to persist leads to accumulating technical debt.

6. Principle of Mutual Distrust

Every component in a distributed system must assume that any upstream or downstream service can fail, so defensive measures are required at each point.

7. Persistence

Persistence converts transient in‑memory data into durable storage such as databases or disks.

8. Critical Section

A critical section is a shared resource that only one thread may access at a time; other threads must wait.

9. Blocking / Non‑Blocking

Blocking occurs when a thread waits for a resource, while non‑blocking allows multiple threads to proceed without waiting.

10. Synchronous / Asynchronous

Synchronous calls block until a result is returned; asynchronous calls return immediately and notify the caller later via callbacks or other mechanisms.

11. Concurrency / Parallelism

Concurrency interleaves execution of multiple tasks on a single processor, whereas parallelism runs multiple tasks simultaneously on multiple processors.

Architecture Design

1. High Concurrency

Design systems to handle many simultaneous requests, typical in high‑traffic scenarios.

2. High Availability

Architectures aim to minimise downtime through redundancy and fault‑tolerant design.

3. Read‑Write Separation

Separate read‑only replicas from write‑primary databases to improve scalability.

4. Cold / Hot Backup

Cold backup keeps a standby server offline until needed; hot backup runs active/standby replication for rapid failover.

5. Multi‑Active Across Regions

Deploy independent data centres in different locations that all serve live traffic.

6. Load Balancing

Distribute traffic across multiple servers to avoid single points of failure and improve capacity.

7. Static‑Dynamic Separation

Serve static assets (HTML, CSS, images) separately from dynamic content to optimise performance.

8. Clustering

Combine multiple servers into a cluster, each node providing the same service to increase throughput.

9. Distributed Systems

Split a monolithic application into independent services that communicate over the network.

10. CAP Theory

In a distributed system you can only guarantee two of Consistency, Availability, and Partition Tolerance.

11. BASE Theory

Provides a practical approach to eventual consistency, availability and soft state for systems that relax strict ACID guarantees.

12. Horizontal / Vertical Scaling

Horizontal scaling adds more nodes; vertical scaling upgrades a single node’s resources.

13. Parallel Expansion

Add nodes to a cluster to increase capacity without downtime.

14. Elastic Scaling

Automatically adjust the number of instances based on real‑time load.

15. State Synchronisation / Frame Synchronisation

State synchronisation centralises game logic on the server; frame synchronisation lets clients run the same simulation steps in lock‑step.

Network Communication

1. Connection Pool

Reuse pre‑established connections to avoid the overhead of creating new ones.

2. Reconnect on Disconnection

Detect network glitches and restore the session once connectivity returns.

3. Session Persistence

Ensure that a series of related requests are routed to the same backend instance.

4. Long / Short Connections

Long‑lived TCP connections stay open for multiple requests; short connections close after each request.

5. Flow Control / Congestion Control

Flow control prevents a fast sender from overwhelming a slow receiver; congestion control avoids network overload.

6. Thundering Herd Effect

When many threads wake up simultaneously for the same event, only one proceeds while the rest go back to sleep, wasting resources.

7. NAT

Network Address Translation maps internal IP addresses to external ones for internet access.

Fault and Exceptions

1. Crash

Unexpected termination of a host or service, including database deadlocks.

2. Core Dump

When a program crashes, the OS may generate a core dump containing memory, registers and stack information.

3. Cache Issues (Penetration, Breakdown, Avalanche)

Cache penetration queries non‑existent data; cache breakdown spikes on hot‑key expiry; cache avalanche occurs when many keys expire simultaneously, overloading the database.

4. HTTP Errors (500‑505)

Various server‑side errors indicating internal failures, unimplemented features, bad gateways, service unavailability, timeouts, or unsupported HTTP versions.

5. Memory Overflow / Leak

Out‑of‑Memory errors occur when allocation fails; memory leaks retain allocated memory, degrading performance.

6. Handle Leak

Unreleased file descriptors cause resource exhaustion.

7. Deadlock

Multiple threads wait indefinitely for each other’s resources.

8. Soft / Hard Interrupts

Hard interrupts are immediate hardware signals; soft interrupts are deferred processing handled later by the kernel.

9. Spike (毛刺)

Transient spikes in CPU, I/O, or network usage that can trigger downstream issues.

10. Replay Attack

Re‑sending captured packets to impersonate a legitimate client.

11. Network Island

Partial network partitions cause inconsistent data across a cluster.

12. Data Skew

Uneven distribution of cached data leads to overloaded nodes.

13. Brain Split

Cluster nodes become isolated, each serving divergent state and causing chaos.

Monitoring and Alerts

1. Service Monitoring

Observe system, application, business and user layers to detect anomalies early.

2. Full‑Link Monitoring

Includes service probing, node health checks, alarm filtering, de‑duplication, suppression, recovery notifications, aggregation and convergence.

3. Fault Self‑Healing

Automatically diagnose, recover and close the loop with surrounding systems.

Service Governance

1. Microservices

Decompose an application into independent services communicating via lightweight protocols such as HTTP/REST.

2. Service Discovery

Register services in a central registry so that clients can locate them dynamically.

3. Traffic Shaping

Use queuing, rate‑limiting or multi‑level caching to smooth bursty traffic.

4. Version Compatibility

Design APIs and data formats to support both old and new versions.

5. Overload Protection

Detect and mitigate load spikes before they cause cascading failures.

6. Circuit Breaker

Temporarily stop calls to an unhealthy service to prevent system‑wide collapse.

7. Service Degradation

Gracefully reduce functionality under high load to preserve core operations.

8. Rate Limiting

Restrict request rates to protect downstream services.

9. Fault Isolation

Remove faulty nodes from the cluster to keep the rest healthy.

10. Testing Methods

Include black‑box/white‑box testing, unit/integration/system/acceptance testing, regression, smoke, performance, benchmark, A/B, and code‑coverage testing.

Release Deployment

1. Environments (DEV / FAT / UAT / PRO)

Separate development, feature acceptance, user acceptance and production stages.

2. Gray Release

Roll out new features to a subset of users before full deployment.

3. Rollback

Revert to the previous stable version when a deployment fails.

Additional Resources

Various links to open‑source projects, interview questions, and further reading are provided throughout the article.