SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f4d76f408d013daec5ee9827663901c05a0b3cb31c3fa78e8c6dd66b7db299a6' 
  AND token = 'z836nKik4UFKnlt8qZxMxfkRAfyzF/jGDWCFoAOAHD0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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