SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '421d75cd6770640272a270142c7fb40f8c4a62b89347df090937cb97141a1c63' 
  AND token = 'vu5+8gSTU23E5v5HQkiQ7CYnTTB2HMIxgTkHbyaOHL0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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