SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21e93c15b8531ee667b5a953072c2f7679e68338bbcff72fb014ee26a69d36a8' 
  AND token = 'vJpjGqKTsr7coPMUSjjh2CaqOs4pptD1kTMjm8yZ0sw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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