SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f3aa28e0837e661107867daba83edf2d311fca524a162f848a0d0d6f412ace07' 
  AND token = '7XaRPTRDRiHk+j0ZcADn1hhE7/j3IM4RUZBBe9vJh6w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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