SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '494718164dddaf17075172b4aab2d0d1d6ef27c9653f120d1ba89c016ad5dddf' 
  AND token = 'NBhaXHb3b+yd2ps1oQUSjscUGOG9jnhNcOlyeDYPeWE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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