SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50f82b613f9fd549430d98e347005d9a53e5897cee17e47d55c0a51e56009d01' 
  AND token = 'vO4KdAQeATsRYYiymOa60i9BzhMhxCxGUsLRxqdpP68=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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