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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '56a21bde8eed9fb307ef9dbd5634d7a54314c811dea9eb57ebcd0b2e25bdcffe' 
  AND token = 'FAN0yO+mPoiJ0BbthOi7ZQkyTLc6TtygE1YOZbKpuWQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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