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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '608b249ebb0ac69a2514e7a84e3557b08cc12dedbb45f7e061baa05c2095daab' 
  AND token = 'vOVK6gWA4PiRt2IE9vOQ8oBcPvyuPUYmcJoDaIJkH2s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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