SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2d51e251bc303d0b2eadcb51494ef9696f914a970b8d6f5af73513e8143f286d' 
  AND token = 'q5Kzh7G7Uq3+iOsckjJlzPKj3Z9cVc0CtU96qFZAjFg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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