SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '73696ae41adb5940cb11e55871672375e8e97307dcad0cb0b4e56e724b34fe4f' 
  AND token = 'iZZwRvBIT9PJ+C2YQQGnyE3+8bVOpaHPmPoXnwI8mG0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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