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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e4752ebd603ea8ce8553c0e8f5c42e574e35671775e44b0f9fde7551b1c18413' 
  AND token = 'epyM5D8nq6XhJEVf6E6qI/mVfZ5jg8zHiWpVBDKcsMA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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