SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a3f1cf138b22d13867a3270f344bf34e043b53657318cc91f4c903abb0a69d46' 
  AND token = 'YKRR25uL/sOKrs6VrOcnXdddL7gSijv/RuHHvjOnROg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

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