SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b0d53589b5d30681c44c1a2bc6b9a74274e281f9498e731fba125950b4fcf288' 
  AND token = 'q/DrNjQHXswR7OfO2mD+88TOVrzoQhpwVo/5llCPo0o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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