SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '735f79c61f9f2162cc2a9603e1eceae3cea41e1058d41065c3fffc9aa3950283' 
  AND token = 'miiYhAjPWIOF9KSVKoKNzRokQ0chujDCu8efbIvL3XQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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