SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51f3db9cc2f4825155952a97bb2eaea94b41c6cd219607cb22aca32c27156299' 
  AND token = 'bnupIpNoMgTthrNbGKfipiJ7mozu2wbREW2GPZEIhWY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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