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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '721817af32ab88c6d359af4c03bd478c43e781a52af60508dacbbbcbf0dec26d' 
  AND token = 'j+7zOZrIAK6UBMIHvHZNtEUItBSiIAY7emlgU+owoHg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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