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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd46c9a453abaa4ab522d10936e39c4a1c66f5f3da203e4a1a79e2946dc4850ca' 
  AND token = 'tNUjdOw4TwxS5NeyLlRFDgZ2kDuTQr5QFFj+Gf2dmF0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00052

JSON explain

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