SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6f8a1956e950fef9cb856e07058e4f10985fee7cd9783dac8471769b40f543bb' 
  AND token = 'hRkOcH0sE9I/bEv/Ag27qysABb4fNA92tIGF+WZnnlk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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