SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '843d359ceb4c5759b61cafa6320408928a21b1498f479fe86d6913af8cba6d57' 
  AND token = 'T/7x8+UR1ZZkKLV/2kwcpY0PX+fRnzndjKogn0KZnGI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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