SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '776df35ce69892561bf085978b0e7d9302fb97f9cb07137df0fdefe39136cc3a' 
  AND token = 'SJLNQAPYEe0TDiDtVEHLj7pDyc+kBeaQJTcKXW6i//0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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