SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8668a2a4fbea288f5c8a363b75e933078db6079bcccdac97f2da36fd2c4fb81' 
  AND token = 'mgRkwGB03ypLRrYVfxie2+ZS9gNrBnKdFl7V2QzYgiA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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