SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21e1a6dc5af90ab6076c01235420d44c4518a4a5dc4f260580777d8973a960c0' 
  AND token = 'WwX8wqc2QiZhDuNgZEHoQa9ku42WkKelNptq0rrXogM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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