SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8d21de86423aadc1c9e0d7c756dbda583b1bb44d08aa199b0930e2977e994bf1' 
  AND token = 'CRBcKOks+dMHo6DqmeBvl4U0zZuG/AiQtvwvQ315JVM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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