PingsNest is an open-source observability and reliability platform for cloud APIs and serverless applications. It functions as a unified control plane that integrates APIs, serverless fleets, dependencies, telemetry, SLO budgets, security audits, and automated operations. The platform is designed for modern cloud environments that span API Gateways, Lambda functions, event buses, message queues, external endpoints, and multiple AWS accounts, addressing the fragmented views that traditional monitoring tools can create. PingsNest monitors API Gateways, serverless functions, and downstream dependencies. It provides telemetry for REST, HTTP, and WebSocket protocols, including P99 tail latency and route table discovery. For serverless environments, it offers a function catalog, cold-start detection, execution duration tracking, and memory tuning. The platform includes synthetic uptime probes for global HTTP/HTTPS checks and SSL certificate health. It automatically discovers relationships between AWS Regions, API Gateways, routes, Lambda targets, and downstream queues. Route-level SLOs, error budgets, and burn rates are tracked, and the platform implements CLOSED, OPEN, and HALF_OPEN fault isolation states to prevent cascading failures. PingsNest also supports native OTLP span ingestion for distributed tracing, CloudWatch log stream integration, AI Diagnostic Scans, security auditing for exposed secrets and IAM policies, and Lambda memory execution cost profiling. Use cases include unifying observability across distributed cloud runtimes, investigating production incidents by correlating metrics, logs, and traces, managing service level objectives, and optimizing serverless resource spend. The workflow involves automatically discovering infrastructure components and relationships, monitoring real-time performance metrics such as P50, P90, and P99 latency, error rates, and cache hit rates, and enabling transition from high-level metrics to specific request and execution events. PingsNest supports 24/7 incident notifications through Slack, PagerDuty, Webhooks, and Email, and provides automated remediation workflows for API spikes, Lambda timeouts, and budget burns. The platform requires AWS credentials setup for integration and is available as an open-source tool.