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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8ef21be1c1be701c4024282af38f41f012e854bd9cb3cfb36950f7e720a1fd6b' 
  AND token = 'iMGk8KPkBROJtII5jB+PRiw6EtfhrJZvHQ4NHSLmm+o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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