SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cf8763c959921830686803ea54360c4dbff2af2f0cae9ba9ee74b1fed6734127' 
  AND token = 'sWd4RYezKITb7VOmXHmhfrqRKijikFpMI4GQIAtJP3c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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