SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '275750033e808af1fbca5514089729bd1670f917435284458bf3c26326d849e0' 
  AND token = 'aBXQrgw3ICOWQ9xVlj/GcDVpKhVMNSi/ZMvSTHMxZUw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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