SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '88d1702a493def903d02429830cc8ba7041e67aae7fe38b42f4607316da62d71' 
  AND token = 'f8hPbCYuXF2PM5CyhzPVka2uxCnmepsp3cXSTCKK/HU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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