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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c40f5b381386d6ac1fdaa384fabfd705a623bb0b7aa1edb5f674870a4025d3bd' 
  AND token = 'R0PWdeCWQbxG6MJo3SedH1ZhaZ3Jxo2at+4DmKkgYio=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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