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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b785bdfca807df88bf7bebd62219ebb6fb75df303b2f3821e3efe2d501ae70f2' 
  AND token = 'j3MjpNrg/D/dnq+WUH58Gy9MTlWyFaZjqaiA4hp6EAM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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