SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '57a7b592c02e7865386ae94528f16e24622a896ef3015db3082b214a59335f83' 
  AND token = '8S9WVNDpTktq5SJJxjgtucVaQjmyensProfqbp6xcCc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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