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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '373a938de9bcbf7dc46b0fa888ca6ff0d813b5d3d573bfb1f0ae6837fd793b23' 
  AND token = 'RiWvzVrJOZ1ZZ2FeLk/bkJRp01eY3b2/xJwOao1+vn0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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