SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cf88b78620b380de3837121b35ee79e82f4673cee44d69c5001e3734818c5946' 
  AND token = 'w0+Zhnq0uzDuWU9X1MRZAVha+yEnncPDAo3ziXW4344=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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