SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c176a1ffa501dafe4749ca3e019f375bca064a517e4cdd0d652d93c0b9358755' 
  AND token = 'ls+G1nywJl4qfoBWVDxzbpE4T3Hcb+y/oACDhhTyXEg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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