SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5203dda7de793b4b8ea01eb8d313644ef70211935843bb185597916547ca6b91' 
  AND token = 'dDXb+X1LNCiagr6ngLwJJTR3Ikw5DTFhss9EGD27RGw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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