SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '258938983645f068ea8ee43c6696b1736432749291fe84fe3aa39235b57b5be0' 
  AND token = 'sVVMPG/Jr+tRrw2bx40quDd5ygGWusMYNEVfJfWoD80=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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