SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '43354f4eb4044a2e8f55115867b5d549b567389b4b0b6a8ec14011ddcf3853af' 
  AND token = 'Kiaga8T+XStA2k2CM09LZscNrD2srJV+UFkROSayJVk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00053

JSON explain

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