SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b30518297e02521ee6394aa5dcc435b41d0b574e334d72d766674e0158792e42' 
  AND token = 'p4s6P3CtfhDiUnibFi+0TF91dHujz3p9BlvfrGcTods=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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