SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51af53d5835f40f6bf92d67ae9da31f5b83e972feb6bebe404c11563af79abdf' 
  AND token = 'g0HThZ8cMDRCsQsFdTs1kZpaaTRo8VTv9c2STJntLcU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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