SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '20c7a43cc12a946d6a9e04c77427b1549673e8520a481737cc2d51a72970ca0f' 
  AND token = 'pskhPiNJAEtfHcXBlAR/ncEtt42+3Jke5IDkZaX/Gz4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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