SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e79384224d5958decf845506e285731ff89d5a1037bf2e27909d814c4aca369b' 
  AND token = 'z/uPxLdHIdgrujxkCTQ1qMkwNgKkRxY5BjrZmhomVp0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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