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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b9be30dd803f92e233750714e695cb102b0b10d6df60da3cb259078a369db47f' 
  AND token = '551EAiseGAtLafp8XoNFe0bSx4k+AttpCeFYqvX8xKk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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