SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '419412a72c8b692690360f2688fb0055a6347e711c8200fe953048afd271398c' 
  AND token = 'xQ3wLR3dOw4DTGzsOFAWuxfgXCHt1COrUCAbrreuNQY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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