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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1678496a5c39a86dd9f37decac3844618b79edde51247a0de6732d6f0ad1fc36' 
  AND token = '8xhGKTgXc29KvowNNqS94iqMo30aHTS7rUYdbc8BW1s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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