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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'e4bb62f5e32294cf6af27cdbe6f5aad2516db68a1480ef5eb37841e5169a2bf1' 
  AND token = 'txkjiy7GoOqF03PMojygw7mjn4PyVqJsMsnIPTGESXQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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