SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'db68138c671d55f5bfd875f67a3e0ebb6d2b8a53444dd302ccc8a91e379e7fba' 
  AND token = 'dUnzQ7uIMYZFJ3TXjtdyzGpE4JnKLTBa/yEkQHwLHE8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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