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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'ac21d7ab1be041ea8d71f1bbbbe01e9f97013e8719a54343b237020fc10b9159' 
  AND token = 'UwwRWhWPozvQ5MLNK2SsOZLhO66o1IxsbZezT8zQrMY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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