SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '352f612c499bec937d0217e66c07f56355d098b5da9e3961560514f35ec8ba33' 
  AND token = 'QrixxOTKJvH7JGRCq1u/zFix2PW2NgweY5g2NlY5wag=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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