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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a7bedb5b15e4abb57b51431da428ddf086b6590bb246fe31fa76c76901d00b51' 
  AND token = 'LDjcIVcd5aZVE+03oVG6E1HjSHN8cFdjtzIFIErAp7Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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