SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '387ce43f1e8bc283b9455abbed263e7e626883ad4aae417651b484b00cdec0b9' 
  AND token = '/z+1+qHv6jANHqPbK7+v5wprPbZX9NI7xAUcxMYblo8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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