SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '708376a097a03168d53ca78a1ffdf0f52d916ce98f787f3f2403b29091fe5738' 
  AND token = 'ZgQGXjR9Y+RxPHUkI5cnwFSNctqPy8i6cr6eGrGAhmc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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