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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21e4f7b33ea0e2f41d0679cc4d34aff0d8625877ea460525e5b999e81317300c' 
  AND token = 'CsYVQF2lhl0RWekvByoSKCDbff3GrGGxVFsj78NNn4g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00014

JSON explain

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