SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3b8382df0267dfdeb842793a7540c3476637b3959e994a0b3413220bb820c652' 
  AND token = '/K3MGA+YhDyKmTnLbMB6HeZVLz1qfikqT3cZ++vy2nY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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