SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a12d129794f405d61431ff9dd691332a13fafdd57896b1f94542eb4b3a3caf7a' 
  AND token = '2nTwpaqp740XtenPpZ3P8vuc1aMtdmM/ONCA+0AIHj4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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