SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c8c1faf269d397c3f89654a91ef36cbca865028d6a2ce040520574b8619a75bf' 
  AND token = 'dZS0RykJ0g0Eu56fYLphh+HTvk7bFQ/ZQUBoLH4vGVs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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