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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c4befc2851ee05edc68dfb0adb6a2a06bbad4b2dfe861d25398fb4d46ffea3f4' 
  AND token = 'gwoqF7beFinYjrTSJ1Dgp0SE5Z0EyGrxOViZp7ihiNk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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