SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '18e0e028c597876f2a8384a30dd9afdb48b5587be7515145baedd54dd4119557' 
  AND token = '/LCcX1KsE/bewVU9Y7RsHuIhD7Rw4BnVnLwZ7gmJ7+I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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