SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f15b9a958b87b8be810eaa027a35aa6c2c2ea97f502252bb6499ebba07aa7140' 
  AND token = 'MQSdqe/zk+NQF+3FCAAsvwuLblHKbUNGHOIVbB2pTvM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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