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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '28d4b7c14c75ad312bc0dcd35d2348d1e463e8a91f65d52254c11b35227fcde6' 
  AND token = '5k/TntDZJadg9ypcPhUDmFHR4/ji+squrAhkPhxcoMc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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