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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'be3e8f1b3ab9ca91ddf3a02b74e01e7df9da3fb98f4694b845ce51bcf669a87f' 
  AND token = 'eRd4tCVvzlSA3oHLcsoUAC2lFrLuGlHEV0VnZYuJnUY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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