SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '611dd284686ead915ad4790010246c0af630db3d2ca7360bca1114fb3f1a3121' 
  AND token = 'n8MAnddZOKkrl9UvlZ04CQKyMn9qm7OajSaY+X6wNE4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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