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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6eeea5a6aec1f51b898c187cb2bde23ab6375ddffe0534f8d0c4e88fec98cc4c' 
  AND token = '5cpDyqgMQAPACmRGbKW0nJZVJ7paPq0ORlRn3TGS+Xg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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