SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '252b073b087569843cdbc3547f6404f63b0bf4699437ed3f011c12f65b5b9c26' 
  AND token = 'VI+pV9e0MidFmkXDIHoUwpCT0PKkhwVElgLHeYp1G+A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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