SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5b8afffe3b4a785cac729aa5fef41e8d29a7a56c218d6950f7998a56f8aa87dc' 
  AND token = '6URUOPfiNASJKHgDS27JYwIYKEdmjLQvu/lg/X0I0+4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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