SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f473e0a66e1681fe039754f04d006555ffd91f59abaef56f93d75d5c438eeffa' 
  AND token = '0gi18u4Xd54pNeObR0kj5K6PPdE1NRvCLRpkwcwnRlE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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