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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76390267821f7d3d68c30eaf7cda5290ee56c3c1bbfeee9e0d80e74aef35fdb3' 
  AND token = 'y5RA9xJTnqU1pmJOFLQkPJhWcH5dFQQ9aZTGv34Gk/4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}