SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '575fddeb5d55affb4a59eec04218d4308407f719da738123f424d0cd9657afd9' 
  AND token = 'V/4mpNtPCBKEA3u/zLvBrqezedoGMSk15gXyxxft7V8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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