SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ef0c892ec7f238816b4dce142537fa797a470f16a9278e7f452e1496f775f8f6' 
  AND token = 'f5EYBECVSfhd3jZeXdWNgpoYdqRs871eRDdt0GBnGjc=' 
  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"
    }
  }
}