SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ec6388aafc81a7d07ef6cddf6b05318c3f73f05f6d1848b8bc6b8ceeb320d71d' 
  AND token = 'InqlvQJtan0bzSPTF2TkwzWlYvkLXTwjYbt/LZOuE1k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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