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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '308ad42df218d6e8fe478e1c79046f6eca221d9f209b72339047c7e79e8e1baa' 
  AND token = 'JjH1zSI1Z1jmkcmFYYWsL53SEnz28tT0awFWqI8zQ68=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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