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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6fc011b0ef4ac38835631aa28ee917295f3451b84695e433a02b0cf0ccaf0d7' 
  AND token = '2+HAR+AaMjQdmFJIRnfSckx1oiLan1jwB2jWaxbN4nY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00015

JSON explain

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