SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '921a9ce39869f7190837c879390789aec4d6ea7a37dee802b3c68d7845ff1a89' 
  AND token = 'hywLY/qv57zCYq7gZp9yxWFhuot/BK+6LF56xM00qPQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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