SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68fb2112896e507b30679e099d76890e6b3bf5d31b32d16a3c756a1b336ad817' 
  AND token = 'rXfgJQQxejTNS0kuxuLLiADDnRmAyGPFsrb3430YTsc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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