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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6f1417200419b3c1a6f93fa1f0c793e7e2ae5ca1e01494427bb0a4be45e519d0' 
  AND token = '4R+SjRcW4hSPLWa4lWSF1dyyu7PURlOFSZ+rc5Gxlzs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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