SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '678b120ca7c856e42d7601880a049568fc55148a2bd3984bf2388442ef50aaa3' 
  AND token = 'sQwIw9SlVGjVq+fk9GUZqszHCpGm3ZhKzv47mpgu2x4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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