SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f50515c886bcb334142a597601e842aa6cd9217cae36df0bf738b23e1ca83a11' 
  AND token = 'i7kVLc8qDDT/SpaCL8eODw5+413hCpZpS0AM/DIcreI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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