SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c6f2f65273bb94b49102b2a0e3cc7204f02a71ee85f76d46397b35d1da6e8f11' 
  AND token = 'HF0myi5imILK71lmldtSBRLziBOMCSjIebQLFqEmOLA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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