SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '71e6250d855b46974acdcb12f71b0490b93d112437ec5231320a2364854cb6a7' 
  AND token = 'qxTTQndpwp18HHpfAKkKCENmfGLtziMQJaWEfn5ueQI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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