SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51b8fdb4025e02b012c295c0b16a56029e3851b33c06b009914ff7e31a45ac39' 
  AND token = 'ukjl6Ncj9UhRJO5hM5SRl8q2GNvkGI4gPygEKuJkY1o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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