SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '99121fc76e549c7afe2f553cfb00cff9673ce51395026e3695d8531003906141' 
  AND token = 'wiPCK0FQZtytYG6+vXxXWcPMsynYQ4l3l+Mps3mw3ek=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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