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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50e84491ec18981b81ed630fc94e48efff4e4ff71fdbee6d64b392ba5b06b1b5' 
  AND token = 'EJbfV7EwyQ/zndeJ7QKRkuxTjbabrNslSAKzCE9Zmd4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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