Practical infra coding

Real tasks from DevOps and SRE coding rounds. Grouped by pattern and tagged by role. Practise each one on LeetCode and tick it off here.

0 / 50 solved

Easy 0/14·Medium 0/31·Hard 0/5

Problem	Difficulty	Practice	Explanation	Solution
Count status codes and top 3 paths in an nginx log	Easy	—	Read	—
Count errors per minute, including quiet minutes	Easy	—	Read	—
p50 and p95 latency per endpoint	Medium	—	Read	—
Stream a huge log: top clients by requests	Medium	—	Read	—
Group Java stack traces by root cause	Medium	—	Read	—
Count log levels per service in JSON-lines logs	Easy	—	Read	—
Pair START and END lines to find slow and stuck requests	Medium	—	Read	—
Alert on a burst of 5xx responses in a sliding window	Medium	—	Read	—
Merge time-sorted logs from several hosts	Hard	—	Read	—
Flag IPs with repeated failed SSH logins	Easy	—	Read	—

Problem	Difficulty	Practice	Explanation	Solution
Flag Kubernetes workloads with missing resource limits	Medium	—	Read	—
Join a host inventory CSV with a team owners CSV	Medium	—	Read	—
Flatten a nested JSON config into dotted keys	Easy	—	Read	—
Diff two JSON configs by key path	Medium	—	Read	—
Find full disks in a metrics CSV with bad rows	Easy	—	Read	—
Parse a small YAML inventory without a YAML library	Medium	—	Read	—
Deep-merge layered config files	Medium	—	Read	—
Find untagged resources in Terraform state	Medium	—	Read	—

Problem	Difficulty	Practice	Explanation	Solution
Total file size per extension under a directory	Easy	—	Read	—
Find duplicate files by content	Medium	—	Read	—
Find files not modified in N days	Easy	—	Read	—
Rotate logs and keep the last five	Medium	—	Read	—
Directory sizes like du, in one pass	Medium	—	Read	—
Compare two directory trees like rsync --dry-run	Medium	—	Read	—
Apply a daily, weekly and monthly backup retention policy	Hard	—	Read	—

Problem	Difficulty	Practice	Explanation	Solution
Fetch every page of a cursor-paginated API	Easy	—	Read	—
Retry an HTTP call with exponential backoff	Medium	—	Read	—
Respect a 429 Retry-After header	Medium	—	Read	—
Aggregate paginated JSON from a local HTTP server	Medium	—	Read	—
Classify HTTP endpoints as up or down with urllib	Easy	—	Read	—
Reconcile DNS records against a desired state	Hard	—	Read	—

Problem	Difficulty	Practice	Explanation	Solution
Build a tail -n clone with argparse	Medium	—	Read	—
Write a du-style disk usage summary	Medium	—	Read	—
Write a config linter that exits non-zero on errors	Medium	—	Read	—
Check a .env file against .env.example	Easy	—	Read	—
Build a JSON query CLI with argparse subcommands	Medium	—	Read	—

Problem	Difficulty	Practice	Explanation	Solution
Find unattached volumes from a mocked cloud API response	Easy	—	Read	—
Report instances missing required tags	Medium	—	Read	—
Flag security group rules open to the internet	Medium	—	Read	—
Break down cloud cost by team tag	Medium	—	Read	—
Plan a safe cleanup of stale snapshots	Hard	—	Read	—

Problem	Difficulty	Practice	Explanation	Solution
Debug labels leaking between calls (mutable default argument)	Easy	—	Read	—
Debug a retry loop that never backs off	Medium	—	Read	—
Fix a broken log-rotation script	Medium	—	Read	—
Find the file handle leak in a log scanner	Medium	—	Read	—
Debug a health check that always reports unhealthy	Medium	—	Read	—

Problem	Difficulty	Practice	Explanation	Solution
Health-check 100 URLs in parallel with a worker limit	Medium	—	Read	—
Make a counter safe to update from many threads	Easy	—	Read	—
Producer/consumer log pipeline with a bounded queue	Medium	—	Read	—
Run commands in parallel with per-command and overall timeouts	Hard	—	Read	—

Must-do problem (the last-minute revision list). Company tags appear only where a public interview report names that company.

Log parsing and aggregationThe most common practical round: count, group and rank log lines.0 / 10