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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6976510434a072ab0905f0d1435dfce0be8c654f0407b90742fbfdfc069b0c0' 
  AND token = 'AImYjs0FEHvMvY5wPVivE71Ql/QukFcNUD2f5vIiCPw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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