SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e21e8b78c5773f149925c8dcefe94ef5687b87c8f15b938dd925ea76c94309ca' 
  AND token = 'VuTAJ2szg2L1MZoXqYiDVu+4ExnD0B8vD6bj3V+ZXN8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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