SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '42a2bb6d2d3be84a21ad00577602fb304ab374412ba190deb46dfa667f10250d' 
  AND token = 'khtkd8qxypq6ULNUrcxr0cRJP9IMror+4PDZtFXVbPw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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