SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a3e337c17861a748066416d58538c09090f8fa2dc5e928711fdf5668816352e8' 
  AND token = 'LQjNpApgDC+ru0st/J5VfxlTRANgwR0yhunS5si0lwA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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