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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b3fa53657fc1d4eb5138ac8d557af4c9a185cdb1046d4397cc515f19df6033e3' 
  AND token = 'C6Pc+Mlkgkf9SmRnNU5CwHLpfUjjrV2ICxA4jBKMNi0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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