SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1440f8fcd65030223824f0547a8daf974891223f89072539fff02a392cf2671e' 
  AND token = 'tvs2niQl4WBAdzykUlD6tHsLIgNBH7ZjpH/gLFv+gWg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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