SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50adf8d813a69d47451eafbebd8addd482b7bf42f328ca3f0bffeb7aeee7523e' 
  AND token = 'rmifMXOwba6+tYh7CaZOPj+kmk1ChUp1UGN5i0ysgiQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00040

JSON explain

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