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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '0468b48cd7fd0604541901889a4d081739dbcf9afb7e9631003c0b0abb404aa7' 
  AND token = 'n0Ca6Cc/V4Tub3kNs/5N2BjnfKJJGxMsY3tSc7Xkhb8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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