SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '35a5698c77e12e7b3e56c1b9831f0ea2fd3c0b7cacf3cb5b69f6c56ad9de4031' 
  AND token = 'sMVz4NwTO+g/0LHL/P7lu3Gpq2ioZbXDCIiHjG+fbJ8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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