SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7717c4f3b74885673acabee2876b625ed3f5950410b2aadbe5649e90719aa319' 
  AND token = 'ejZlT+4uGmxxMACdcxjWY/pFytUgPRS2qqYrWLV+2II=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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