SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c79ff5a92b7894810e4970a19a70380ae145179ed4f50e2a08bf66842515aa8c' 
  AND token = 'Jrsemd/vm2xD5d2I7xVQZDWrRxDJuYIJ3fCPb34uZRk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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