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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50f080a2e361e70c5015d0ddf2b1c1f3c3c67728f36dd45d2022b0ad46b7c794' 
  AND token = 'hsxtVdUzJkKgHRlb2ZiP4rpB39msoAy77/5ObhB8EaQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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