SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3451fea6552045683ae797599810c6cfe195517fca7b15888a75aa6af0e6d757' 
  AND token = 'INu7xhwJtYb68MtVMW+PXf/IyF2pLbmK+/LCLEeXp8c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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