SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4e1be18119c32e8437f3091e9f82f3a93fefee4b7259069b2ce35fe2520e6888' 
  AND token = 'mRIyKzJ8PNU+oHkymYMaEkBfBC35+6qYAI4ANMIY3jw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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