SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a34b4c7ac0c47a1b00f42fba369bd8499ab92b61824b1fcec21fa24e15f5175d' 
  AND token = 'upicVtGRsnObO8xfKLlaLc9iyoERn6/snGMG32iES8M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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