SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '90b26ffdb37bfee1d5caeef970280e9292580ed35007bc14ad11cbe30d1aa849' 
  AND token = 'rtEThRzlJR0FzwKLOo3jCxSK7PeKbc2cPgSskBejq0E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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