SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f8a7d1afc54c0cccdab81e78c9bf76ccbdad611fed15c55ddb1f31445b2cc709' 
  AND token = '52ua/rcOEzA9T7/MIuA/0D7hmklFevsWyasWyWV4Yeg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}