SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '812a06067d94815f86863c398f400c7b462014955303b4465fa3fa71e2821e91' 
  AND token = 'LKo4L+I7iTnjlFerxkzjCtPTzbwBoOLKGSsHEeer8HM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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