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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c4ed3e7354a85c0d3228e47929f5e04a819236c7e4f7dbb5bbfbeeae56338333' 
  AND token = '1iimrTY/A5QFECq9LCt6Zdh2bGQnhJ6AiBc0+/sYQcw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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