SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '40b366b2b84915fa53555e4854786d621b2830719365dc3676267aeb0a5f9a40' 
  AND token = 'r6nsPJq4o1XPMxQ74IqMHxwXOz0zn55/hIofvHH+7x8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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