SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '4df87319292fada98deb43f0bda3fb703cd0bd4aa32c52d68dcf916b15f4099a' 
  AND token = 'DeJGKl/R/IatDmisd6n7SYmmmJbLhzK68Zo9vmq32U0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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