SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c492a81b5cda58d6253b1357fa4d15959955f42c1c0f7678ccdcc3404f666c15' 
  AND token = 'WAqZgYENUzkF1p/NuJMsKzocvKUf6GHfsTosJRBNZ0o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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