SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '75b29d67814923adb6da97643e92699f1c5138c61cd8bfcfb04b5a9c6a6172ef' 
  AND token = 'xUnxJhQQYCfLHyTC9EKC5SqzV0PzfIZdBnYEl0nNczY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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