SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1838fb5ef044f7beec5eb114d4e764530759b9d0a593b20fcf380ee8d1ba66ca' 
  AND token = '+MsJppmTD1/+EJwRsEDruGAC8XLNNhtqU47ZBwVR8Ec=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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