SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e978fa78346f74c03b6dfc180de59b68dcc33e826d83c0f18f797eae3026b192' 
  AND token = 'ZgYhkBJ0Ew+nmse6AQ+3QerHFmQG5XIGuVTfKGLPjMo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00038

JSON explain

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