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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c99d490631a45e4d78ff25cb9392a0b1233d39a54ecc3f7d4bd0edaf3c25397f' 
  AND token = 'RnDRx001ac7kdbw5ZiCFOd+3Uj7A/gVSdRdHlyJORz0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00052

JSON explain

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