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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '257312323df4374aed81858611b407faa147fc07881db70f7afa6a18cefba87f' 
  AND token = 'vQZUT+ISfhhaAR7GLsllRkfm712fdoG5RNgQhW60vwE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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