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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '31cd14dd785f7844f042f3cee34e8b7da19df1cf71299143ddbee8f8bbf6d760' 
  AND token = 'mpohgyVURgRm9aTNXs8bQzwgFlywn6Pq+oxNoK4nAqI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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