SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '787fea1fc21f2b40e2b40b58edc00589b213cc17085526e66d6edc4fbf912312' 
  AND token = 'bcWt3V+FCFRBfgS+Lk2tUlcVxslccmR8tBPmcGd5xwM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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