SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '84a896356d0a69b2fc350169de7508934592022939bb8810bde69c2141296db9' 
  AND token = 'hxzy5LLn9jYO09pBxBbYUTTD9jSVFmo4uvFsPFvxJTE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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