SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '815b54b43a668457ff7eac83254890afba8f321a62f9751d95b9ddf646cf0528' 
  AND token = 'gDrO29L3x1OI8IMgJ3xinP1akW2xhsOoBRUvhSwJu5s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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