SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'eb50ec23711d1e19fc35db4b3995be1f84b30cdd8248c3bc405f54da28110c62' 
  AND token = 'UIuWDGhPROThs710LlcRp8QrG8HcjujGsneLdcOdubg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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