SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b890727bf8be8026d56fafd2ee3b3436f26466f1db928d7e1843f376b18a4aa3' 
  AND token = 'dG+GmJhaXzrRVQE31ooHsiEr39TeqE8CR4JLkSMHKQI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00056

JSON explain

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