SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6a252f88618b8022cb0ff57de23e0e7eabe9c9fd7b6edaef820a0ba149a79b5d' 
  AND token = 'Is18gO7l44dDqF9vVbEDEdQ8pTBraZBDE/QHddXt+ok=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}