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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f4521bfc30b25455471f4b8571b7bf254e19ffa3e4da595a63196442d262e522' 
  AND token = 'ugsmhdrSvZbyDZaHaBt3h+0yif9im1fIup49sOL0JQk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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