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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8a1b1bc4a3d7fc5925ad13111c31aa33479061289ff09c9f410392e27380e5e' 
  AND token = '+8XD0Lb4QUEkxqb/PR9mp5roSQ8O0Tf4snibvhQ4+Qg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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