SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5a824a83c3570f96e9a9ea7849068ae8d520e3455e8262be15378809e5643349' 
  AND token = '+qAH1gbucoekDZe4PrdjbAm67qP3oLMf6UPncweYoQc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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