SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '388039aa7a91c5860e968769906592e07e84fb73a1651530b7810c7c316ed69e' 
  AND token = 'FPK9QGS+s+dWL63WW+5OWGr42xMoGXR7Sn+pcs9Jlu4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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