SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8f3edf73f20fd8f2a1581a6de9458d9947705e62e6600cf799425b5748a0dd61' 
  AND token = 'g2OLXtjsZuTjeVyqt6U73vd/5iTlvWapwYRe+F2frLg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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