SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '506a68014d8e3ae43256ae1e9e0840a2fe6ba5a745b3ab572cb9496534716d98' 
  AND token = 'ADEudy+dA3iCQkzPpoVzAQM3WpiMTooM6fpKR0/rjWg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00052

JSON explain

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