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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '71e9d30d6a530f695118678b4f92dfee6d49e36c30e749adb3bb1a68e2cbfd47' 
  AND token = 'My7orBXdn1k4920KhwiRQcm3hbl15VMqaPHfpj+3clU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00045

JSON explain

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