SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '753ef9f8e959f45cee44d05c625d0416a6d0757dd62e6acce412ff9297f55593' 
  AND token = 'XDHq+3JwRy5sEAktsmdyxPbj/EXZ6+6oNzP3VV56W9s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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