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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8dc968ded2d6df30e4e01a64ce70ca3aa5e9087a41c6b0b0e238621bbfe3b673' 
  AND token = '8UeswLmx0QmNkb1gWq7/JqYCgawC5LTHadeD7STft04=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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