SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3f9c430b273e54db6b665416b2b8786d5d3ab9ec9cc543601f89954177503d71' 
  AND token = 'SzEFZfSXWDo/BUMt49Kn+OGKLmClMvgKlCq90Kv5eVE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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