SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '39b150110a12f4a8855bebf16545bf1b6778860ad723a6e84d43ec7b4b21a879' 
  AND token = 'GqCp1KV+bkzVun0hEnmrxZABDOaDqqxwf/4vyvH3Qx0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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