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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8b8d5dcca4fbadebedf61101bca1e57fdbf7e702427e6a04d81a8177274975a7' 
  AND token = 'XRUju7ZWUo5nWfXhi3OvWhd+GhISkt5kNeo3svbH+3M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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