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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1257a16a5f2a2ba1c204b6bbabf1f8627e1389549ec66d1998e8f77f27e99f98' 
  AND token = '4lbTqY14ejjci9qKuV4NAK6HLZ0BElcmtgatljJQQQA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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