SELECT 
  1 
FROM 
  cscart_june_setuplock_keys 
WHERE 
  key_id = '76fce887314e04c24c3931da660c513c612fde4428579d616f88b61a9c86e1d2' 
  AND token = 'zR7i79YqujKt0Mbn+Yxoa/qbBKXuct/aWkgF+LR5V30=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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