SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fc499c7aa64d25f5ac43954d05be926dda9172ee9fed994a6c8c1d2878e63119' 
  AND token = 'UlXGFtq2S5Y6yQ3nWfYF1jr63T0D+1maiu8i4uh9r1I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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