SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e81daccc36f6f33e674e82bd3b12c4b75341ab3e3a48fb946143315da68be2e4' 
  AND token = 'WDAvO3zkyQEwv2c2Un4DMBYqMcgloGjgf7dpKFm/hVI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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