SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c03ee994cee155c685b0deed3cb8cd5f8ce7dad36a465014fe311b188f1d7052' 
  AND token = '83BdiK2RnTEhvKuRfJ54PkNBjTzXae0Eq3KGjz3Gb2s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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