SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6a52802d3c45e7f642fee63bae02b337ed0a0d0f72e20154d1046c5e728be46b' 
  AND token = 'cvSelgltJk+tIlRDamKmeykBeEqg+uc8HJteo21WAyk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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