SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4b0521e5d8e4931ac12739c4661a55914c9bc8b19894485d0ff8db2239a9cf7c' 
  AND token = 'LI+rYoimXYrzpSRkTZIqgllUqNwHvA8qEjmA1KkLC+o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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