SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '126caf5b49e4e8878bb1103679bfde8ecd4fcc82a4387ad73f0940e932bc5008' 
  AND token = 'BHjQxhFEc1GB2LozdUVBgK7fYktXzt5WVrG+JI54EHw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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