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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c761d7a1ecd757e21c96c9c9b11ec39dd04b009657edfe0ecbdff385513d43f6' 
  AND token = 'z5iEUIhIiF3RMHJ9Mac+DqeM7s6NVFi3CxpfaJnI1b4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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