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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81bf31ef90bb3db67852b2c300a37964006cefb18dd224de27e2e38d280b6b57' 
  AND token = 'zUun2ikYr6Fy2sfjmH0kEU5MvOvlsbblMVEoz+k6vgE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}