SELECT 
  1 
FROM 
  cscart_aprillock_keys 
WHERE 
  key_id = '121d5c966f8598932e2655067a7500bca0cb7f5d471201b81f3de02a31ab15c5' 
  AND token = 'eHxMpN3u3fXFwzt+x19lygg9I6naBMqVCk1VlAtL7A4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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