SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21dfcc39a2ae85480cf6ab23727f5ae3c126e3d971c84634474f32432a6399a6' 
  AND token = 'UlNgU+UkgrvRepgr9GghBnRYjMj2dzR+Lqlxxgyj+Ms=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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