SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '833ec5444533781eff524e212e98de53612c1f9511abd5456ebd9c793611c70d' 
  AND token = 'icmjtzLR3OhJTuBn0wthZ8UV0kq5UlS9Jpf1XNBs1Yw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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