SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '29c21afa80ce6a25ee11c1857c3ebb3797a4a5f2a848c4b73db40030b41b1903' 
  AND token = 'NR1OzpvaUeKccihRF33bEi81JF/MhYryZ/4l7/F2wgk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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